Configuring glibc with CFLAGS="-g1" causes glibc to be built without the
--noexecstack option:

$ ../libc/configure | grep noexecstack
checking whether --noexecstack is desirable for .S files... yes

$ ../libc/configure CFLAGS="-g1" | grep noexecstack
checking whether --noexecstack is desirable for .S files... no

Other variants of the -g option (-g, -g0, -g2) give the correct behaviour.

This happens because the configure script is doing an invocation of gcc like the
following:

$ gcc -g1 -S conftest.c
$ gcc -g1 -c conftest.s -Wa,--noexecstack
test.s: Assembler messages:
test.s:79: Error: file number 1 already allocated

This fails for a reason other than the -Wa,--noexecstack argument, but it causes
configure to conclude that --noexecstack is not available.  I filed a bug on gcc
(http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35925) because it was not clear
whether passing -g1 to both invocations should be expected to work.

One way to fix this is not to pass CFLAGS to the second invocation; using
ASFLAGS brings this into line with other compilations of .s files.  Suggested
patches attached.