From: Ben Hutchings <ben@decadent.org.uk>
Date: Sun, 21 Feb 2016 15:33:15 +0000
Subject: tools/build: Remove bpf() run-time check at build time

It is not correct to test that a syscall works on the build system's
kernel.  We might be building on an earlier kernel version or with
security restrictions that block bpf().

Also fix the test for whether __NR_bpf is defined.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/tools/build/feature/test-bpf.c
+++ b/tools/build/feature/test-bpf.c
@@ -9,6 +9,7 @@
 #  define __NR_bpf 321
 # elif defined(__aarch64__)
 #  define __NR_bpf 280
+# else
 #  error __NR_bpf not defined. libbpf does not support your arch.
 # endif
 #endif
@@ -28,9 +29,5 @@ int main(void)
 	attr.kern_version = 0;
 
 	attr = attr;
-	/*
-	 * 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));
+	return 0;
 }