AC_LANG_FUNC_LINK_TRY(C): stub detection fails with ICC 10.1

[Aaron Ucko]

I have observed that AC_FUNC_LINK_TRY(C), which serves as the guts of
AC_CHECK_FUNCS, can inappropriately return "yes" for functions which are
merely stubs when building with version 10.1 of Intel's C/C++ compiler
(ICC) on x86_64-linux-gnu systems (and perhaps also other versions).
AFAICT, the reason for this incorrect behavior is that its <limits.h>
has truly minimal dependencies, such that no glibc header ever actually
makes it in.

I have worked around this problem in the project that most concerns me
by checking for ICC and temporarily adding -Wl,--fatal-warnings to
LDFLAGS prior to invoking AC_CHECK_FUNCS.  However, for a long-term fix,
I would suggest explicitly checking for <gnu/stubs.h> and having
AC_FUNC_LINK_TRY(C) generate code that directly #include-s it if
available.

Could you please look into the matter?

Thanks!

-- 
Aaron Ucko <ucko at ncbi>, NCBI C++ Toolkit core development group