perf tools: Fix PowerPC native building

Checks BPF syscall number, turn off libbpf building on platform doesn't
correctly support sys_bpf instead of blocking compiling.

Reported-and-Tested-by: Naveen N. Rao <[e-mail]>
Signed-off-by: Wang Nan <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Cc: Sukadev Bhattiprolu <[e-mail]>
Cc: Zefan Li <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/build/feature/test-bpf.c

···
+#include <asm/unistd.h>
 #include <linux/bpf.h>
+#include <unistd.h>
+
+#ifndef __NR_bpf
+# if defined(__i386__)
+#  define __NR_bpf 357
+# elif defined(__x86_64__)
+#  define __NR_bpf 321
+# elif defined(__aarch64__)
+#  define __NR_bpf 280
+#  error __NR_bpf not defined. libbpf does not support your arch.
+# endif
+#endif
 
 int main(void)
 {
 	union bpf_attr attr;
 
+	/* Check fields in attr */
 	attr.prog_type = BPF_PROG_TYPE_KPROBE;
 	attr.insn_cnt = 0;
 	attr.insns = 0;
···
 	attr.kern_version = 0;
 
 	attr = attr;
-	return 0;
+	/*
+	 * Test existence of __NR_bpf and BPF_PROG_LOAD.
+	 * This call should fail if we run the testcase.
+	 */
+	return syscall(__NR_bpf, BPF_PROG_LOAD, attr, sizeof(attr));
 }

tools/lib/bpf/bpf.c

···
 #include "bpf.h"
 
 /*
- * When building perf, unistd.h is override. Define __NR_bpf is
- * required to be defined.
+ * When building perf, unistd.h is overrided. __NR_bpf is
+ * required to be defined explicitly.
  */
 #ifndef __NR_bpf
 # if defined(__i386__)