M1 Python

[DanAlbert]

Subtask for #1299

[rprichard]

I think our Python3 is already a fat binary:

$ file /x/ndk/prebuilts/python3/darwin/bin/python3.9
/x/ndk/prebuilts/python3/darwin/bin/python3.9: Mach-O universal binary with 2 architectures: [x86_64:Mach-O 64-bit x86_64 executable, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL|PIE>] [arm64:Mach-O 64-bit arm64 executable, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL|PIE>]

https://android.googlesource.com/platform/external/python/cpython3/+/24cdfe16599af4bed00f790584d696493c45afab/kokoro/build.py#57:

    if host == Host.Darwin:
        sdkroot = env.get('SDKROOT')
        if sdkroot:
            print("Using SDK {}".format(sdkroot))
            config_cmd.append('--enable-universalsdk={}'.format(sdkroot))
        else:
            config_cmd.append('--enable-universalsdk')
        config_cmd.append('--with-universal-archs=universal2')

        MAC_MIN_VERSION = '10.9'
        cflags.append('-mmacosx-version-min={}'.format(MAC_MIN_VERSION))
        cflags.append('-DMACOSX_DEPLOYMENT_TARGET={}'.format(MAC_MIN_VERSION))
        cflags.extend(['-arch', 'arm64'])
        cflags.extend(['-arch', 'x86_64'])
        env['MACOSX_DEPLOYMENT_TARGET'] = MAC_MIN_VERSION
        ldflags.append("-Wl,-rpath,'@loader_path/../lib'")

[DanAlbert]

We're shipping the one from prebuilts/ndk/python

$ file ../prebuilts/ndk/python/darwin-x86_64/bin/python
../prebuilts/ndk/python/darwin-x86_64/bin/python: Mach-O 64-bit x86_64 executable, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL|PIE>

It's also still Python 2 to support GDB. In r24 we can drop that since we dropped GDB. For r23 we may need to ship both, or just allow the small part of the build where ndk-build is running Python to be Rosetta.

[enh-google]

For r23 we may need to ship both, or just allow the small part of the build where ndk-build is running Python to be Rosetta.

are you planning on "backporting" all the universal binaries to the r23 LTS then? i was actually assuming we wouldn't (unless something drastic happens, like devices shipping without Rosetta2 while r23 is still "the" LTS)?

or did you just mean "r23 will have both python2 and python3 for different reasons" and i'm reading too much into this because of the specific bug title? :-)

[DanAlbert]

are you planning on "backporting" all the universal binaries to the r23 LTS then?

I was planning on at least trying. We have a compatible toolchain available. Unless making make/cmake/ninja M1 compatible ends up being invasive getting those four components to support M1 does most of what anyone actually cares about, I think. The rest of them are less interesting though since they're not in the build hot path.

[DanAlbert]

We have python 3 in the NDK already at toolchains/llvm/prebuilt/linux-x86_64/python3/bin/python3, so we should be able to fix ndk-build to use that instead of python 2.

[DanAlbert]

I think the only change we need to cherry pick for r23c is https://android-review.googlesource.com/c/platform/ndk/+/1892798