versioner: compile with `clang -include foo.h -`.

At least one warning only triggers in files that are included, instead
of being passed directly. Switch to compiling with -include, and fix
the resulting warnings.

Bug: https://github.com/android-ndk/ndk/issues/474
Test: mma -j && versioner
Test: python tools/versioner/run_tests.py
Change-Id: I784698c18540c9cc30f372f279a1cec1d75721ea
diff --git a/libc/include/wchar.h b/libc/include/wchar.h
index c9a78be..a86c8a9 100644
--- a/libc/include/wchar.h
+++ b/libc/include/wchar.h
@@ -42,6 +42,11 @@
 
 __BEGIN_DECLS
 
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability-completeness"
+#endif
+
 wint_t            btowc(int);
 int               fwprintf(FILE *, const wchar_t *, ...);
 int               fwscanf(FILE *, const wchar_t *, ...);
@@ -134,6 +139,10 @@
 wchar_t* wcsdup(const wchar_t*);
 size_t wcsnlen(const wchar_t*, size_t);
 
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
+
 __END_DECLS
 
 #endif /* _WCHAR_H_ */