multilib build is broken

[Sven Joachim]

Since the 20160521 patchlevel, the multilib builds in the Debian package
fail.  First, configure complains about the CC variable:

,----
| checking whether gcc -m64 accepts -g... yes
| checking version of gcc -m64... 5.4.0
| checking for gcc -m64 option to accept ANSI C... none needed
| checking $CC variable... broken
| configure: WARNING: your environment misuses the CC variable to hold 
CFLAGS/CPPFLAGS options
`----

This is wrong, since "gcc -m64" actually invokes a different compiler
than gcc, so putting -m64 into CFLAGS would be a misuse.

Later, configure fails:

,----
| checking for native build C compiler... gcc
| checking for native build C preprocessor... ${BUILD_CC} -E
| checking for native build C flags... 
| checking for native build C preprocessor-flags... 
| checking for native build linker-flags... 
| checking for native build linker-libraries... 
| configure: error: Cross-build requires two compilers.
| Use --with-build-cc to specify the native compiler.
`----

I have set BUILD_CC=gcc, specifying --with-build-cc=gcc instead of or in
addition to that makes no difference.  Full build log is attached.

Cheers,
       Sven

build.log
Description: ncurses build log