setting compiler, compiler flags and linker flags from rpmmacros

Hello all,

I am trying to recompile some fundamental packages (glibc, XFree86, Qt, 
GTK, Gnome, KDE, etc) for better performance using the intel C++ and 
Fortran compilers. I was wondering if there was a way to set the flags 
from rpmmacros? Here are the compiler flags I want to set globally, so 
as to not require my having to change this information in each .spec file:

CC=icc
CXX=icc
F77=ifort
LDR=icc
CFLAGS="-O3 -axWK"
FFLAGS=$CFLAGS
CXXFLAGS=$CFLAGS

in the .spec files these flags are set in the %build section.

Tanim Islam