[Bug libstdc++/81542] Compilation failure with math.h and -D_GLIBCXX_USE_C99_FP_MACROS_DYNAMIC

[gmc at synopsys dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81542

--- Comment #3 from Gordon Mc <gmc at synopsys dot com> ---
GCC build being used, was configured with --enable-bootstrap
--enable-threads=posix --disable-checking --with-system-zlib
--enable-__cxa_atexit --disable-libunwind-exceptions
--enable-languages=c,c++,fortran --disable-libgcj --with-cpu=generic
--build=x86_64-redhat-linux
Thread model: posix