firestore.cmake: point to the HEAD of the NanopbNoPackedStructsCmakeFix branch in the iOS repository

[dconeybe]

DO NOT MERGE

This is a temporary branch that picks up firebase/firebase-ios-sdk#8923 (CMakeLists.txt: add -DPB_NO_PACKED_STRUCTS=1 to the nanopb compiler flags) from the iOS SDK. With this, I'm going to create a custom build of the C++ SDK so that the customer can test to see if it fixes #712 ([Bug] Firestore fails to link for desktop on macOS Monterey because of unaligned pointers).

[dconeybe]

I've started a "CPP binary SDK packaging" action at d74c415:

https://github.com/firebase/firebase-cpp-sdk/actions/runs/1420069216

Update: The build failed with a bunch of errors like this:

/tmp/tmp.wAGqMiTvUy/merge_analytics.sh: No such file or directory

[dconeybe]

I've merged in the latest from the main branch and started a "CPP binary SDK packaging" action at 0f77498:

https://github.com/firebase/firebase-cpp-sdk/actions/runs/1421892145

Fingers are cross that this will fix the "merge_analytics.sh: No such file or directory" errors.

[dconeybe]

Turns out, the merge_analytics.sh build error was actually a symptom of an earlier build error that was silently ignored:

CMake Error at /home/runner/work/firebase-cpp-sdk/firebase-cpp-sdk/out-sdk/external/tmp/firestore-gitclone.cmake:40 (message):
  Failed to checkout tag: '9aa0c85b1817684a601c21dcabe8bfe8e74c3692'
make[2]: *** [CMakeFiles/firestore.dir/build.make:99: src/firestore-stamp/firestore-download] Error 1
make[1]: *** [CMakeFiles/Makefile2:307: CMakeFiles/firestore.dir/all] Error 2

I'll double-check that I used the correct commit hash and try again.

[dconeybe]

Ahh, the problem is that firebase/firebase-ios-sdk#8923 was merged into master and the branch was deleted. So the commit is no longer valid. I'm just going to use the head commit from right now: firebase/firebase-ios-sdk@03e174c

[dconeybe]

Okay, I've updated the pinned commit to the current head of the iOS SDK and started a a "CPP binary SDK packaging" action at 44e348a:

https://github.com/firebase/firebase-cpp-sdk/actions/runs/1426820775

[dconeybe]

Closing since the C++ SDK v8.8.0 (released yesterday) contains the fix hacked in by this PR.