I'm trying to provide a compiler to this macro (using it's name and
the full path name) when some special conditions occur but as it isn't
on the default $PATH, AC_PROG_CC skips it.
Right now, I can only find two solutions. Just add the the directory
that contains this compiler to the $PATH or set CC (in the configure.ac)
with this compiler when those conditions happen.
First approach isn't quite user-friendly because each time I want to
run configure I have to touch the PATH variable. The latter would skip a
new compiler given by the user through CC environment variable when
invoking configure.