According to Pat:
make[1]: Entering directory `/usr/local/gcc/gcc-2.8.0/p/rts' ../../xgpc -B../../ --automake -c -DGPC -Wall -Wpointer-arith [...] gpc1: installation problem, cannot exec `gpc': No such file or directory
That's a bug in the AutoMake mechanism: It looks for `gpc' in order to call it recursively, but doesn't find it because there is only an `xgpc'.
To work around, try with a symbolic link "gpc -> xgpc" in `/usr/local/gcc/gcc-2.8.0'.
(At least this is a different error that I got trying the gpc-980330 version!)
That's at least some progress! ;-)-:
Good luck,
Peter