Speed up iOS CI build

[jfirebaugh]

The iOS build is topping out our build times at 30+ minutes.

We should investigate how to bring this down to the range of other builds (10-15 minutes).

Here's one thing to try: https://labs.spotify.com/2013/11/04/shaving-off-time-from-the-ios-edit-build-test-cycle/

[1ec5]

A typical CI build produces a fat dynamic framework compiled for five architectures (arm64, armv7, armv7s, x86_64, i386). Additionally, make test-ios appears to be recompiling everything from scratch even after the call to make ios. We should make sure both rules are using the same build settings and depend on the same derived data location. I’m working on ensuring identical output directories in #4641 for the non-gyp-managed projects, because until now, command line and GUI builds haven’t been sharing the same output directory.

Use plain “DWARF” instead of “DWARF with dSYM File” as your “Debug Information Format”.

We do use “DWARF with dSYM File” as the debug information format, but build rules other than make ipackage-sim use the Release configuration, which means we need a dSYM to symbolicate crash reports.

Don’t compile your project code or use static libraries compiled with -O4 since it tells Clang to enable Link Time Optimizations (LTO) making the linking stage much slower. Use -O3 at most.

We don’t use -O4. The core targets use -O0 for Debug builds and -O3 for Release builds. In #3183, I changed the iOS targets to use -Os for Release builds, drastically reducing the size of the build.

[jfirebaugh]

Until we can build iOS on CI infrastructure that supports parallelization across a build matrix, I think we should limit per-push builds to a single architecture and target configuration. Since we want to run tests in the simulator, this should be the architecture that the simulator requires (x86_64 I assume) and the configuration that is most useful if the tests fail (Debug).

[1ec5]

👍 So we should bring back the old make isim and invoke that instead of make ios on Bitrise.

[jfirebaugh]

Well, I was thinking more of changing make ios to do what make isim did. In general, I think it's useful to have CI be make <platform> && make test-<platform> consistently across the platforms.

[jfirebaugh]

the architecture that the simulator requires (x86_64 I assume)

Surprisingly, this appears to be i386, not x86_64.

[jfirebaugh]

Down to ~500 seconds with these changes. 🎉