iOS: remove desktop sources that were mistakenly merged into app/CMakeLists.txt

[arizigler]

Description

Since latest Xcode (13.3) and clang++ (apple 13.1.6) iOS apps can no longer compile as the linker complains about undefined symbols:

Undefined symbols for architecture arm64:
  "firebase::AppDataDir(char const*, bool, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*)", referenced from:
      firebase::(anonymous namespace)::GetFilename(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >&) in firebase(heartbeat_date_storage_desktop.cc.o)

Taking a deeper look it seems like there is indeed an undefined symbol in firebase.xcframework:

         U __ZN8firebase10AppDataDirEPKcbPNSt3__112basic_stringIcNS2_11char_traitsIcEENS2_9allocatorIcEEEE

While searching for this symbol in the repo it seems to be defined in a file called app/src/filesystem_apple.mm and indeed it's not part of iOS source files in app/CMakeLists.txt.

It's not clear what has changed in Apple clang++ 13.1.6 compared to Apple clang++ 13.0.0 but somehow the former throws the aforementioned undefined symbol error.

There are 2 possible fixes, AFAIK:

1. add filesystem_apple.mm to iOS sources in the CMakeLists.txt file.
2. remove heartbeat_date_storage_desktop.cc and heartbeat_info_desktop.cc as they're not needed by iOS build.

I took the second approach as it seems to me this has been a mistake slipped in through the merge (which can as well be wrong).

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Testing

Built my app with the patched version on Xcode 13.3 and it managed to compile and work as expected.

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Type of Change

Place an x the applicable box:

• Bug fix. Add the issue # below if applicable.
• New feature. A non-breaking change which adds functionality.
• Other, such as a build process or documentation change.

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Notes

• Bug fixes and feature changes require an update to the Release Notes section of release_build_files/readme.md.
• Read the contribution guidelines CONTRIBUTING.md.
• Changes to the public API require an internal API review. If you'd like to help us make Firebase APIs better, please propose your change in a feature request so that we can discuss it together.

[google-cla]

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For more information, open the CLA check for this pull request.

[jonsimantov]

Hi @arizigler,

Thanks for the fix, nice catch!

Could you please follow the instructions in this comment from google-cla to allow us to include your PR?

Thanks again!

Jon

[arizigler]

Hi @jonsimantov,
Glad I could share my little contribution to your awesome project. Keep up the great work you're doing!
I believe I followed the cla guidelines and passed the cla automatic check. Can you please verify?
It says now it is only blocked because it needs a reviewer.

[github-actions]

✅  Integration test succeeded!

Requested by @jonsimantov on commit refs/pull/868/merge
Last updated: Sat Mar 19 20:53 PDT 2022
View integration test log & download artifacts

[jonsimantov]

Approved assuming integration tests succeed.