UnixWare glims 5 7.1.1 i386 x86at SCO UNIX_SVR5

When ./configure runs with CC=gcc in the environment, the package configures 
and builds without errors, but each program crashes with 'out of memory' errors.
Even 'testparms /dev/null' crashes in this way.

When ./configure runs with CC=cc, the configure process ends up writing 
#define HAVE_COMPILER_WILL_OPTIMIZE_OUT_FNS 1
in source/include/config.h.
The package doesn't compile then. When I manually update config.h after 
configuring (to exclude that line), the package compiles and runs fine.

I know unixware is old, decrepit and needs to be avoided, but I'm stuck with it 
here at work for at least another few months.