Set Locale to English when uppercasing strings to match Enums

[jin]

Fixes #5157

If a user's default system locale is not en, en_US or en_UK, there may be a chance that String#toUpperCase will result in a string that does not exist in the Enum declaration. This is the case in #5157.

To fix this, it's either

1. setting the Locale in the individual toUpperCase calls or
2. set Locale to English by default from Bazel.java.

I chose the first because it seemed less intrusive, but I'm open to suggestions.