raid6: test: only check for Altivec if building on powerpc hosts

Altivec is only available for powerpc hosts, so only check for its
availability when the host is powerpc, to avoid error messages being
shown on architectures other than x86, arm or powerpc.

Signed-off-by: WANG Xuerui <git@xen0n.name>
Link: https://lore.kernel.org/r/20230731104911.411964-6-kernel@xen0n.name
Signed-off-by: Song Liu <song@kernel.org>

lib/raid6/test/Makefile

@@ -35,6 +35,12 @@ ifeq ($(ARCH),aarch64)
         HAS_NEON = yes
 endif
 
+ifeq ($(findstring ppc,$(ARCH)),ppc)
+        CFLAGS += -I../../../arch/powerpc/include
+        HAS_ALTIVEC := $(shell printf '$(pound)include <altivec.h>\nvector int a;\n' |\
+                         gcc -c -x c - >/dev/null && rm ./-.o && echo yes)
+endif
+
 ifeq ($(IS_X86),yes)
         OBJS   += mmx.o sse1.o sse2.o avx2.o recov_ssse3.o recov_avx2.o avx512.o recov_avx512.o
         CFLAGS += -DCONFIG_X86
@@ -44,15 +50,10 @@ ifeq ($(IS_X86),yes)
 else ifeq ($(HAS_NEON),yes)
         OBJS   += neon.o neon1.o neon2.o neon4.o neon8.o recov_neon.o recov_neon_inner.o
         CFLAGS += -DCONFIG_KERNEL_MODE_NEON=1
-else
-        HAS_ALTIVEC := $(shell printf '$(pound)include <altivec.h>\nvector int a;\n' |\
-                         gcc -c -x c - >/dev/null && rm ./-.o && echo yes)
-        ifeq ($(HAS_ALTIVEC),yes)
-                CFLAGS += -I../../../arch/powerpc/include
-                CFLAGS += -DCONFIG_ALTIVEC
-                OBJS += altivec1.o altivec2.o altivec4.o altivec8.o \
-                        vpermxor1.o vpermxor2.o vpermxor4.o vpermxor8.o
-        endif
+else ifeq ($(HAS_ALTIVEC),yes)
+        CFLAGS += -DCONFIG_ALTIVEC
+        OBJS += altivec1.o altivec2.o altivec4.o altivec8.o \
+                vpermxor1.o vpermxor2.o vpermxor4.o vpermxor8.o
 endif
 
 .c.o: