Don't set the +x bit by default on WriteFile().

This change is a spiritual successor of https://bazel-review.googlesource.com/c/7410/ . That one had a merge conflict and it was small enough that a rewrite was easier than updating it.

RELNOTES: None.
PiperOrigin-RevId: 160251282
diff --git a/src/main/cpp/util/file_platform.h b/src/main/cpp/util/file_platform.h
index 31a0d1c..179eac3 100644
--- a/src/main/cpp/util/file_platform.h
+++ b/src/main/cpp/util/file_platform.h
@@ -97,7 +97,7 @@
 // Writes `size` bytes from `data` into file `filename` and chmods it to `perm`.
 // Returns false on failure, sets errno.
 bool WriteFile(const void *data, size_t size, const std::string &filename,
-               unsigned int perm = 0755);
+               unsigned int perm = 0644);
 
 // Result of a `WriteToStdOutErr` operation.
 //