versioner: refactor to use CompilerInstance directly.

This will make it easier to switch over to a virtual filesystem,
which should drastically improve performance.

This also fixes an issue with warning/error reporting.

Bug: http://b/32748936
Test: python run_tests.py
Change-Id: I2e967acf75db29c95f3a03f4f94cccd22c367ad5
diff --git a/libc/include/signal.h b/libc/include/signal.h
index a9df04b..17bc57d 100644
--- a/libc/include/signal.h
+++ b/libc/include/signal.h
@@ -29,12 +29,13 @@
 #ifndef _SIGNAL_H_
 #define _SIGNAL_H_
 
+#include <sys/cdefs.h>
+#include <sys/types.h>
+
 #include <asm/sigcontext.h>
 #include <bits/pthread_types.h>
 #include <bits/timespec.h>
 #include <limits.h>
-#include <sys/cdefs.h>
-#include <sys/types.h>
 
 #if defined(__LP64__) || defined(__mips__)
 /* For 64-bit (and mips), the kernel's struct sigaction doesn't match the POSIX one,