Postgres on Sun Solaris 2.5.1

We are trying to upgrade our present Postgres 6.3.2 database running on
Linux/i386 to v6.4.2 on Sun Solaris 2.5.1.
I tried to compile the server using GCC for Solris 2.5.1. Everything
went well except while running the regression tests, which failed giving
these messages:
+ ERROR:  Load of file
/bytek/postgres/postgresql-6.4.2/src/test/regress/input/../regress.so
failed: ld.so.1: bytek/postgres/bin/postmaster: fatal: relocation error:
symbol not found: SPI_tuptable: referenced in
/bytek/postgres/postgresql-6.4.2/src/test/regress/input/../regress.so
+ ERROR:  Load of file
/bytek/postgres/postgresql-6.4.2/src/test/regress/input/../../../../contrib/spi/refint.so
failed: ld.so.1:/bytek/postgres/bin/postmaster: fatal: relocation error:
symbol not found: SPI_result: referenced in
/bytek/postgres/postgresql-6.4.2/src/test/regress/input/../../../../contrib/spi/refint.so

I had set up the PGLIB and even the LD_LIBRARY_PATH to the postgres lib.

Moreover some of the functions I had written to implement triggers using
SPI failed to compile in GCC on Solaris (ld fails with fatal signal 6,
while linking the shared object file) although they had compiled on GCC
on Linux.

My question is which compiler has been used to test the port of Postgres
on Solaris 2.x. Or to reword it : Can I use GCC to compile Postgres on
Solaris?

Sorry for being verbose,

Thanks,
Anand.