selftests/bpf: Enable test test_progs-cpuv4 for gcc build kernel

Currently, test_progs-cpuv4 is generated with clang build kernel
when bpf cpu=v4 is supported by the clang compiler.
Let us enable test_progs-cpuv4 for gcc build kernel as well.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20230728055745.2285202-1-yonghong.song@linux.devSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/Makefile

@@ -36,11 +36,12 @@ LDLIBS += -lelf -lz -lrt -lpthread
 ifneq ($(LLVM),)
 # Silence some warnings when compiled with clang
 CFLAGS += -Wno-unused-command-line-argument
-# Check whether cpu=v4 is supported or not by clang
+endif
+
+# Check whether bpf cpu=v4 is supported or not by clang
 ifneq ($(shell $(CLANG) --target=bpf -mcpu=help 2>&1 | grep 'v4'),)
 CLANG_CPUV4 := 1
 endif
-endif
 
 # Order correspond to 'make run_tests' order
 TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \