groff: Fix math.h inclusion from system headers issue
groff has system headers overrides in its sourcecode which it
generates as fallbacks but in some cases when a system header includes
math.h via include <> directive it lands in the override header and
causes compile issues, seen with clang+libc++, this patch makes sure
that right defines are available before including it
Signed-off-by: Khem Raj <raj.khem@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
