insert macros within AC_PROG_CC before _AC_COMPILER_EXEEEXT

[Daily, Jeff A]

FYI I'm using autoconf 2.67.

Here's why I need to insert macros into AC_PROG_CC:
I have some users who refuse to use anything but Intel's icc and ifort, version 
8.1.  But, they have a newer GCC installed (4.1.2) which causes icc to barf 
with "invalid GNU version number: 412" (causing configure to report "C compiler 
cannot create executables").  The problem can be worked-around if they add 
CFLAGS="-gcc-version-340".  But these users want me to add this flag 
conditionally during configure.  But how?

AC_PROG_CC expands _AC_COMPILER_EXEEXT once.  This is where the standard test 
fails because of the missing flag.  What I need is to test link (presumably 
using AC_LINK_IFELSE) as soon as the C compiler is found, but before 
_AC_COMPILER_EXEEXT is expanded.

Can this be done?  I'd rather not copy-and-paste my own version of AC_PROG_CC 
and insert the modifications manually (unless that truly is the only way...)  
I'll need to do something similar for AC_PROG_CXX as well.

Jeff