selftests/powerpc: Fix incorrect kernel headers search path

Use $(KHDR_INCLUDES) as lookup path for kernel headers. This prevents
building against kernel headers from the build environment in scenarios
where kernel headers are installed into a specific output directory
(O=...).

Cc: stable@vger.kernel.org # v5.18+
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230127135755.79929-22-mathieu.desnoyers@efficios.com

tools/testing/selftests/powerpc/ptrace/Makefile

@@ -33,7 +33,7 @@ TESTS_64 := $(patsubst %,$(OUTPUT)/%,$(TESTS_64))
 $(TESTS_64): CFLAGS += -m64
 $(TM_TESTS): CFLAGS += -I../tm -mhtm
 
-CFLAGS += -I../../../../../usr/include -fno-pie
+CFLAGS += $(KHDR_INCLUDES) -fno-pie
 
 $(OUTPUT)/ptrace-gpr: ptrace-gpr.S
 $(OUTPUT)/ptrace-pkey $(OUTPUT)/core-pkey: LDLIBS += -pthread

tools/testing/selftests/powerpc/security/Makefile

@@ -5,7 +5,7 @@ TEST_PROGS := mitigation-patching.sh
 
 top_srcdir = ../../../../..
 
-CFLAGS += -I../../../../../usr/include
+CFLAGS += $(KHDR_INCLUDES)
 
 include ../../lib.mk
 

tools/testing/selftests/powerpc/syscalls/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
 TEST_GEN_PROGS := ipc_unmuxed rtas_filter
 
-CFLAGS += -I../../../../../usr/include
+CFLAGS += $(KHDR_INCLUDES)
 
 top_srcdir = ../../../../..
 include ../../lib.mk

tools/testing/selftests/powerpc/tm/Makefile

@@ -17,7 +17,7 @@ $(TEST_GEN_PROGS): ../harness.c ../utils.c
 CFLAGS += -mhtm
 
 $(OUTPUT)/tm-syscall: tm-syscall-asm.S
-$(OUTPUT)/tm-syscall: CFLAGS += -I../../../../../usr/include
+$(OUTPUT)/tm-syscall: CFLAGS += $(KHDR_INCLUDES)
 $(OUTPUT)/tm-tmspr: CFLAGS += -pthread
 $(OUTPUT)/tm-vmx-unavail: CFLAGS += -pthread -m64
 $(OUTPUT)/tm-resched-dscr: ../pmu/lib.c