Add tools/gen_all

Add a script to invoke all the other code generation scripts, namely:
-  fix_include_guards
-  gen_android_bp
-  gen_merged_protos
-  gen_tracing_cpp_headers_from_protos
-  gen_binary_descriptors

Also remove the .py from gen_tracing_cpp_headers_from_protos.py, to
match all the other scripts.

Change-Id: Ibc71110152879ef460363ca02144146c8d83d01e
diff --git a/tools/gen_binary_descriptors b/tools/gen_binary_descriptors
index d608095..2e1b4f1 100755
--- a/tools/gen_binary_descriptors
+++ b/tools/gen_binary_descriptors
@@ -150,6 +150,7 @@
     if not str(e):
       raise
     print('Error: {}'.format(e))
+    return 1
 
 if __name__ == '__main__':
   exit(main())