We were using the `defaults` command-line utility to parse
Plist files, but it was never supported by Apple, and it
appears that in an upcoming OS release, it will be less likely
to work:
> WARNING: The defaults command will be changed in an upcoming
> major release to only operate on preferences domains. General
> plist manipulation utilities will be folded into a different
> command-line program.
Fixes https://github.com/flutter/flutter/issues/37701
Instead of requiring a name_output.sh, expect a file called
.app_filename in the macos/Flutter directory containing just the name of
the application. The expectation is that the Xcode build will create
that file with a script.
This is not intended as a long-term solution, but it's a substantial
improvement over name_output.sh:
- name_output.sh required constructing the full build output path; this
made sense when it was coupled with build.sh, but now that the
decision for where build output goes lives in flutter_tool, that logic
should as well.
- Changing the name of the application required also updating
name_output.sh, which is error-prone. With .app_filename, it can be
created using $PRODUCT_NAME, which means that the usual way of setting
the application name will automatically update this flow as well.
Part of #30706
