bug#38434: QEMU 4.1.1 build is not reproducible

[Ludovic Courtès]

QEMU 4.1.1 does not build reproducibly.  From ‘guix challenge’:

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/gnu/store/i347iqh8a5x7h1lgs6wlvk5jk5cwilgi-qemu-4.1.1 contents differ:
  no local build for '/gnu/store/i347iqh8a5x7h1lgs6wlvk5jk5cwilgi-qemu-4.1.1'
  
https://bayfront.guixsd.org/nar/gzip/i347iqh8a5x7h1lgs6wlvk5jk5cwilgi-qemu-4.1.1:
 09np35221bfpf4spqvnxh6wzb15s1l8vz2vn72kyc41qf02bgq69
  https://ci.guix.gnu.org/nar/gzip/i347iqh8a5x7h1lgs6wlvk5jk5cwilgi-qemu-4.1.1: 
0hp5qc6phcrdncs31brcq5wban25fif4y1kihlsc75zzj2cbakx7
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Here are the differences:

--8<---------------cut here---------------start------------->8---
$ diff -r --no-dereference /tmp/qemu.{1,2}
Binary files /tmp/qemu.1/bin/qemu-system-aarch64 and 
/tmp/qemu.2/bin/qemu-system-aarch64 differ
Binary files /tmp/qemu.1/bin/qemu-system-alpha and 
/tmp/qemu.2/bin/qemu-system-alpha differ
Binary files /tmp/qemu.1/bin/qemu-system-arm and 
/tmp/qemu.2/bin/qemu-system-arm differ
Binary files /tmp/qemu.1/bin/qemu-system-cris and 
/tmp/qemu.2/bin/qemu-system-cris differ
Binary files /tmp/qemu.1/bin/qemu-system-hppa and 
/tmp/qemu.2/bin/qemu-system-hppa differ
Binary files /tmp/qemu.1/bin/qemu-system-i386 and 
/tmp/qemu.2/bin/qemu-system-i386 differ
Binary files /tmp/qemu.1/bin/qemu-system-lm32 and 
/tmp/qemu.2/bin/qemu-system-lm32 differ
Binary files /tmp/qemu.1/bin/qemu-system-m68k and 
/tmp/qemu.2/bin/qemu-system-m68k differ
Binary files /tmp/qemu.1/bin/qemu-system-microblaze and 
/tmp/qemu.2/bin/qemu-system-microblaze differ
Binary files /tmp/qemu.1/bin/qemu-system-microblazeel and 
/tmp/qemu.2/bin/qemu-system-microblazeel differ
Binary files /tmp/qemu.1/bin/qemu-system-mips and 
/tmp/qemu.2/bin/qemu-system-mips differ
Binary files /tmp/qemu.1/bin/qemu-system-mips64 and 
/tmp/qemu.2/bin/qemu-system-mips64 differ
Binary files /tmp/qemu.1/bin/qemu-system-mips64el and 
/tmp/qemu.2/bin/qemu-system-mips64el differ
Binary files /tmp/qemu.1/bin/qemu-system-mipsel and 
/tmp/qemu.2/bin/qemu-system-mipsel differ
Binary files /tmp/qemu.1/bin/qemu-system-moxie and 
/tmp/qemu.2/bin/qemu-system-moxie differ
Binary files /tmp/qemu.1/bin/qemu-system-nios2 and 
/tmp/qemu.2/bin/qemu-system-nios2 differ
Binary files /tmp/qemu.1/bin/qemu-system-or1k and 
/tmp/qemu.2/bin/qemu-system-or1k differ
Binary files /tmp/qemu.1/bin/qemu-system-ppc and 
/tmp/qemu.2/bin/qemu-system-ppc differ
Binary files /tmp/qemu.1/bin/qemu-system-ppc64 and 
/tmp/qemu.2/bin/qemu-system-ppc64 differ
Binary files /tmp/qemu.1/bin/qemu-system-riscv32 and 
/tmp/qemu.2/bin/qemu-system-riscv32 differ
Binary files /tmp/qemu.1/bin/qemu-system-riscv64 and 
/tmp/qemu.2/bin/qemu-system-riscv64 differ
Binary files /tmp/qemu.1/bin/qemu-system-s390x and 
/tmp/qemu.2/bin/qemu-system-s390x differ
Binary files /tmp/qemu.1/bin/qemu-system-sh4 and 
/tmp/qemu.2/bin/qemu-system-sh4 differ
Binary files /tmp/qemu.1/bin/qemu-system-sh4eb and 
/tmp/qemu.2/bin/qemu-system-sh4eb differ
Binary files /tmp/qemu.1/bin/qemu-system-sparc and 
/tmp/qemu.2/bin/qemu-system-sparc differ
Binary files /tmp/qemu.1/bin/qemu-system-sparc64 and 
/tmp/qemu.2/bin/qemu-system-sparc64 differ
Binary files /tmp/qemu.1/bin/qemu-system-tricore and 
/tmp/qemu.2/bin/qemu-system-tricore differ
Binary files /tmp/qemu.1/bin/qemu-system-unicore32 and 
/tmp/qemu.2/bin/qemu-system-unicore32 differ
Binary files /tmp/qemu.1/bin/qemu-system-x86_64 and 
/tmp/qemu.2/bin/qemu-system-x86_64 differ
Binary files /tmp/qemu.1/bin/qemu-system-xtensa and 
/tmp/qemu.2/bin/qemu-system-xtensa differ
Binary files /tmp/qemu.1/bin/qemu-system-xtensaeb and 
/tmp/qemu.2/bin/qemu-system-xtensaeb differ
$ diffoscope /tmp/qemu.{1,2}/bin/qemu-system-aarch64
--- /tmp/qemu.1/bin/qemu-system-aarch64
+++ /tmp/qemu.2/bin/qemu-system-aarch64
├── /gnu/store/mx2bgrpxkbdjsmhlxp9a30hbzcilk4cn-binutils-2.32/bin/readelf 
--wide --program-header {}
│ @@ -6,20 +6,20 @@
│  Program Headers:
│    Type           Offset   VirtAddr           PhysAddr           FileSiz  
MemSiz   Flg Align
│    PHDR           0x000040 0x0000000000000040 0x0000000000000040 0x0002a0 
0x0002a0 R   0x8
│    INTERP         0x0002e0 0x00000000000002e0 0x00000000000002e0 0x000050 
0x000050 R   0x1
│        [Requesting program interpreter: 
/gnu/store/ahqgl4h89xqj695lgqvsaf6zh2nhy4pj-glibc-2.29/lib/ld-linux-x86-64.so.2]
│    LOAD           0x000000 0x0000000000000000 0x0000000000000000 0x2fd3c8 
0x2fd3c8 R   0x1000
│    LOAD           0x2fe000 0x00000000002fe000 0x00000000002fe000 0x60c6f5 
0x60c6f5 R E 0x1000
│ -  LOAD           0x90b000 0x000000000090b000 0x000000000090b000 0x4180b0 
0x4180b0 R   0x1000
│ +  LOAD           0x90b000 0x000000000090b000 0x000000000090b000 0x418070 
0x418070 R   0x1000
│    LOAD           0xd23b28 0x0000000000d24b28 0x0000000000d24b28 0x32eda0 
0x36c760 RW  0x1000
│    DYNAMIC        0xf4ca78 0x0000000000f4da78 0x0000000000f4da78 0x000450 
0x000450 RW  0x8
│    NOTE           0x000330 0x0000000000000330 0x0000000000000330 0x000020 
0x000020 R   0x4
│    TLS            0xd23b28 0x0000000000d24b28 0x0000000000d24b28 0x000000 
0x000238 R   0x8
│ -  GNU_EH_FRAME   0xbe9520 0x0000000000be9520 0x0000000000be9520 0x02f8fc 
0x02f8fc R   0x4
│ +  GNU_EH_FRAME   0xbe94e0 0x0000000000be94e0 0x0000000000be94e0 0x02f8fc 
0x02f8fc R   0x4
│    GNU_STACK      0x000000 0x0000000000000000 0x0000000000000000 0x000000 
0x000000 RW  0x10
│    GNU_RELRO      0xd23b28 0x0000000000d24b28 0x0000000000d24b28 0x22b4d8 
0x22b4d8 R   0x1
│  
│   Section to Segment mapping:
│    Segment Sections...
│     00     
│     01     .interp
├── /gnu/store/mx2bgrpxkbdjsmhlxp9a30hbzcilk4cn-binutils-2.32/bin/readelf 
--wide --sections {}
│ @@ -14,18 +14,18 @@
│    [ 9] .rela.dyn         RELA            000000000000f860 00f860 2e79b8 18   
A  5   0  8
│    [10] .rela.plt         RELA            00000000002f7218 2f7218 0061b0 18  
AI  5  25  8
│    [11] .init             PROGBITS        00000000002fe000 2fe000 000017 00  
AX  0   0  4
│    [12] .plt              PROGBITS        00000000002fe020 2fe020 004130 10  
AX  0   0 16
│    [13] .plt.got          PROGBITS        0000000000302150 302150 000020 08  
AX  0   0  8
│    [14] .text             PROGBITS        0000000000302170 302170 60857c 00  
AX  0   0 16
│    [15] .fini             PROGBITS        000000000090a6ec 90a6ec 000009 00  
AX  0   0  4
│ -  [16] .rodata           PROGBITS        000000000090b000 90b000 2de520 00   
A  0   0 32
│ -  [17] .eh_frame_hdr     PROGBITS        0000000000be9520 be9520 02f8fc 00   
A  0   0  4
│ -  [18] .eh_frame         PROGBITS        0000000000c18e20 c18e20 10a270 00   
A  0   0  8
│ -  [19] .gcc_except_table PROGBITS        0000000000d23090 d23090 000020 00   
A  0   0  1
│ +  [16] .rodata           PROGBITS        000000000090b000 90b000 2de4e0 00   
A  0   0 32
│ +  [17] .eh_frame_hdr     PROGBITS        0000000000be94e0 be94e0 02f8fc 00   
A  0   0  4
│ +  [18] .eh_frame         PROGBITS        0000000000c18de0 c18de0 10a270 00   
A  0   0  8
│ +  [19] .gcc_except_table PROGBITS        0000000000d23050 d23050 000020 00   
A  0   0  1
│    [20] .tbss             NOBITS          0000000000d24b28 d23b28 000238 00 
WAT  0   0  8
│    [21] .init_array       INIT_ARRAY      0000000000d24b28 d23b28 001270 08  
WA  0   0  8
│    [22] .fini_array       FINI_ARRAY      0000000000d25d98 d24d98 000008 08  
WA  0   0  8
│    [23] .data.rel.ro      PROGBITS        0000000000d25da0 d24da0 227cd8 00  
WA  0   0 32
│    [24] .dynamic          DYNAMIC         0000000000f4da78 f4ca78 000450 10  
WA  6   0  8
│    [25] .got              PROGBITS        0000000000f4dec8 f4cec8 002130 08  
WA  0   0  8
│    [26] .data             PROGBITS        0000000000f50000 f4f000 1038c8 00  
WA  0   0 32

[…]
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Ludo’.