get-rusage-data tests: Avoid test failure on musl libc

[Bruno Haible]

On Alpine Linux 3.12, 3.13, I see this test failure:

FAIL: test-get-rusage-data
==========================

../../gltests/test-get-rusage-data.c:60: assertion 'value3 > value1' failed
Aborted
FAIL test-get-rusage-data (exit status: 134)

This patch fixes it.


2021-01-17  Bruno Haible  <bruno@clisp.org>

        get-rusage-data tests: Avoid test failure on musl libc.
        * modules/get-rusage-data-tests (Files): Add m4/musl.m4.
        (configure.ac): Invoke gl_MUSL_LIBC.
        * tests/test-get-rusage-data.c (main): Treat musl libc like glibc.

diff --git a/modules/get-rusage-data-tests b/modules/get-rusage-data-tests
index 0b55794..109cce5 100644
--- a/modules/get-rusage-data-tests
+++ b/modules/get-rusage-data-tests
@@ -1,10 +1,12 @@
 Files:
 tests/test-get-rusage-data.c
 tests/macros.h
+m4/musl.m4
 
 Depends-on:
 
 configure.ac:
+gl_MUSL_LIBC
 
 Makefile.am:
 TESTS += test-get-rusage-data
diff --git a/tests/test-get-rusage-data.c b/tests/test-get-rusage-data.c
index 229fd8c..c626540 100644
--- a/tests/test-get-rusage-data.c
+++ b/tests/test-get-rusage-data.c
@@ -55,7 +55,7 @@ main ()
       ASSERT (value2 >= value1);
       ASSERT (value3 >= value2);
 
-#if !(__GLIBC__ == 2 || (defined __APPLE__ && defined __MACH__) || defined 
__FreeBSD__ || defined __DragonFly__ || defined __OpenBSD__ || defined _WIN32 
|| defined __CYGWIN__)
+#if !(__GLIBC__ == 2 || MUSL_LIBC || (defined __APPLE__ && defined __MACH__) 
|| defined __FreeBSD__ || defined __DragonFly__ || defined __OpenBSD__ || 
defined _WIN32 || defined __CYGWIN__)
       /* Allocating 2.5 MB of memory should increase the data segment size.  */
       ASSERT (value3 > value1);
 #endif