Revert "perf s390: Always build with -fPIC"

This one made x86 always build with -fPIC, when the intention was for
s390 to be built that way, due to a rebase mistake.

Reported-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
This reverts commit 1dc4ddf1.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>