tools headers: Syncronize linux/build_bug.h with the kernel sources

To pick up the changes in:

07a368b3f55a79d3 ("bug: introduce ASSERT_STRUCT_OFFSET")

This cset only introduces a build time assert macro, that may be useful
at some point for tooling, for now it silences this perf build warning:

Warning: Kernel ABI header at 'tools/include/linux/build_bug.h' differs from latest version at 'include/linux/build_bug.h'
diff -u tools/include/linux/build_bug.h include/linux/build_bug.h

Cc: Adrian Hunter <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Maxim Levitsky <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/include/linux/build_bug.h

···
 #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
 #endif // static_assert
 
+
+/*
+ * Compile time check that field has an expected offset
+ */
+#define ASSERT_STRUCT_OFFSET(type, field, expected_offset)	\
+	BUILD_BUG_ON_MSG(offsetof(type, field) != (expected_offset),	\
+		"Offset of " #field " in " #type " has changed.")
+
+
 #endif	/* _LINUX_BUILD_BUG_H */