[android] Remove ICU build flags since that requirement was dropped in #40340

[finagolfin]

Since @Azoy removed libicu as a stdlib dependency, this greatly simplifies the build-script command needed to cross-compile the toolchain for Android. I only removed the Android ICU flags in this pull, but there are other uses for Windows and other platforms that can also be removed. I tested this pull with #35707 by applying the following command that is taken from the Android build preset run on the CI, but removing the flags to build libicu and install the toolchain:

./swift/utils/build-script --release --assertions --no-swift-stdlib-assertions --android
--android-ndk /home/butta/android-ndk-r23b/ --android-arch aarch64 --android-api-level 24
--test --validation-test --long-test --stress-test --test-optimized --lit-args="-v --time-tests"
--build-swift-static-stdlib --build-swift-static-sdk-overlay --build-swift-stdlib-unittest-extra
--host-test --skip-test-linux -j9 --skip-build-compiler-rt

I ran this for both aarch64 and armv7 and only 13 C++ Interop tests failed, which were already broken on the Android CI because of #39605 a couple weeks ago. The good news is those tests progressed further with #35707, but still failed because of some missing headers and other problems with the NDK.

So this pull passes all the same tests as the current Android CI and should be fine. @drodriguez and @compnerd, you two know this code best, please review.

[finagolfin]

We may need this back if we ever add instructions for cross-compiling swift-corelibs-foundation for Android as in #38441, since that repo still requires libicu, but in the meantime this libicu cross-compilation is no longer needed and we can always resurrect this doc from git if we want it later.

[compnerd]

The only thing that I’m remotely concerned about is the foundation test. That still requires icu, but assuming that there’s a different script for that/you’ve tested foundation with this change, this looks great!

[finagolfin]

I just went ahead and got rid of this whole file because it hasn't worked in years. The expanded build preset from #38441 should replace this.

[finagolfin]

This hasn't been used since @davezarzycki removed it in #32042.

[finagolfin]

assuming that there’s a different script for that/you’ve tested foundation with this change

Cross-compilation of Foundation uses this CMake config I added this summer to get the path to a cross-compiled libicu in a different way. I haven't actually now tested this pull with that flag yet butand since they're completely separate build paths, I don't see that gettingthe Foundation linking against a cross-compiled libicu wasn't affected.

Thanks for the quick review.

[finagolfin]

Removed this line that I had missed and rebased.

[finagolfin]

@MaxDesiatov, would you run the CI?

[MaxDesiatov]

@swift-ci please test

[MaxDesiatov]

@swift-ci please smoke test

[swift-ci]

Build failed
Swift Test OS X Platform
Git Sha - a3ea28f

[finagolfin]

macOS CI failure appears spurious, as this pull doesn't affect macOS and the only failure I see is FAIL: Testing swift-docc failed but none of the swift-docc tests failed.

[finagolfin]

@davezarzycki, I see you're up: would you merge if that CI failure isn't required to pass? It is spurious.

[davezarzycki]

I lost my window to work today so I don't have time to review this before merging. Maybe @gottesmm can help.

[finagolfin]

@davezarzycki, this pull was already approved and passed most of the CI, just need someone to merge.

[finagolfin]

Thanks for getting this in quickly, @compnerd.