selftests/powerpc: Force ptrace tests to build -fno-pie

Currently these tests won't build with a `--enable-default-pie`
compiler as they require r30 to be clobbered. This gives
an error:
  ptrace-tm-spd-gpr.c:41:2: error: PIC register clobbered by 'r30' in 'asm'

This forces these tests to be built no-pie.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/ptrace/Makefile

@@ -6,7 +6,7 @@ include ../../lib.mk
 
 all: $(TEST_PROGS)
 
-CFLAGS += -m64 -I../../../../../usr/include -I../tm -mhtm
+CFLAGS += -m64 -I../../../../../usr/include -I../tm -mhtm -fno-pie
 
 $(TEST_PROGS): ../harness.c ../utils.c ../lib/reg.S ptrace.h