libbpf: Add __noinline macro to bpf_helpers.h

__noinline is pretty frequently used, especially with BPF subprograms, so add
them along the __always_inline, for user convenience and completeness.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200820231250.1293069-4-andriin@fb.com

tools/lib/bpf/bpf_helpers.h

@@ -32,6 +32,9 @@
 #ifndef __always_inline
 #define __always_inline __attribute__((always_inline))
 #endif
+#ifndef __noinline
+#define __noinline __attribute__((noinline))
+#endif
 #ifndef __weak
 #define __weak __attribute__((weak))
 #endif