selftests/powerpc/ptrace: Fix out-of-tree build

We should use TEST_GEN_PROGS, not TEST_PROGS. That tells the selftests
makefile (lib.mk) that those tests are generated (built), and so it
adds the $(OUTPUT) prefix for us, making the out-of-tree build work
correctly.

It also means we don't need our own clean rule, lib.mk does it.

We also have to update the ptrace-pkey and core-pkey rules to use
$(OUTPUT).
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/ptrace/Makefile

 # SPDX-License-Identifier: GPL-2.0
-TEST_PROGS := ptrace-gpr ptrace-tm-gpr ptrace-tm-spd-gpr \
+TEST_GEN_PROGS := ptrace-gpr ptrace-tm-gpr ptrace-tm-spd-gpr \
               ptrace-tar ptrace-tm-tar ptrace-tm-spd-tar ptrace-vsx ptrace-tm-vsx \
               ptrace-tm-spd-vsx ptrace-tm-spr ptrace-hwbreak ptrace-pkey core-pkey \
               perf-hwbreak ptrace-syscall
@@ -7,14 +7,9 @@ TEST_PROGS := ptrace-gpr ptrace-tm-gpr ptrace-tm-spd-gpr \
 top_srcdir = ../../../../..
 include ../../lib.mk
 
-all: $(TEST_PROGS)
-
 CFLAGS += -m64 -I../../../../../usr/include -I../tm -mhtm -fno-pie
 
-ptrace-pkey core-pkey: child.h
-ptrace-pkey core-pkey: LDLIBS += -pthread
-
-$(TEST_PROGS): ../harness.c ../utils.c ../lib/reg.S ptrace.h
+$(OUTPUT)/ptrace-pkey $(OUTPUT)/core-pkey: child.h
+$(OUTPUT)/ptrace-pkey $(OUTPUT)/core-pkey: LDLIBS += -pthread
 
-clean:
-	rm -f $(TEST_PROGS) *.o
+$(TEST_GEN_PROGS): ../harness.c ../utils.c ../lib/reg.S ptrace.h