tools/build: Fix bpf(2) feature test (fixes FTBFS on alpha, sh4; closes: #822364)

debian/changelog

@@ -132,6 +132,8 @@ linux (4.5.2-1) UNRELEASED; urgency=medium
     result in file conflicts
   * linux-perf: Move tips.txt to /usr/share/doc/linux-perf-<version>
     (Closes: #821741)
+  * tools/build: Fix bpf(2) feature test (fixes FTBFS on alpha, sh4;
+    closes: #822364)
 
   [ Aurelien Jarno ]
   * [mips*] Emulate unaligned LDXC1 and SDXC1 instructions.

debian/patches/bugfix/all/tools-build-remove-bpf-run-time-check-at-build-time.patch

@@ -6,11 +6,21 @@ 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
-@@ -28,9 +28,5 @@ int main(void)
+@@ -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;