Unable to override flags from templated `xcodeproj.bazelrc`

[luispadron]

Not sure if this is intended, don't think it is because otherwise there doesn't seem to be a way to override this without modifying the template directly.

For example, if we want to set common:rules_xcodeproj --remote_download_outputs=all it doesn't seem like the way the .bazelrc files/flags are loaded allows for this to override the templated common:rules_xcodeproj --remote_download_outputs=toplevel

The issue seems to be in the way the template loads and sets the private _rules_xcodeproj_build config:

...

common:_rules_xcodeproj_build --config=rules_xcodeproj

### Project specific configs
%project_configs%
# Import `xcodeproj.bazelrc` if it exists
try-import %workspace%/xcodeproj.bazelrc

Anything set in xcodeproj.bazelrc or .bazelrc would make it into rules_xcodeproj config but not _rules_xcodeproj_build