Install the Android NDK before all steps that need it

[kendalharland]

Ensure android NDK is installed regardless of runner.

This fixes the workflow on runner images where the NDK is not
installed. It bundles together a few other changes to ensure
CMake is executed correctly and make it easier to diff CMake
log in the GHA UI with the content in swift-toolchain.yml

Changes

• Always run gha-setup-vsdevenv even if runners.os != 'Windows'
  • It provides us with the path to CMake
• Switch to nttdl/setup-ndk to install the Android NDK.
• Always specify Android-specific MAKE defines, but enable others
  iff matrix.os == Android.
  • CMAKE_SYSTEM_NAME=${{ matrix.os }} controls which system we're
    building for, so there's no need to use matrix.extra_flags for
    Android-specific defines. Inlining them ensures powershell
    variable expansion works, and makes it easier to copy paste
    CMake commands for for local reproduction.

Test

• BCNY Cirun: https://github.com/thebrowsercompany/swift-build/actions/runs/9717754718
• BCNY GitHub: https://github.com/thebrowsercompany/swift-build/actions/runs/9717754725

[compnerd]

This has multiple changes, including whitespace changes. Can you please split this up into focused changes?

[kendalharland]

This has multiple changes, including whitespace changes. Can you please split this up into focused changes?

Removed the whitespace changes.

Re the rest of the changes: Unfortunately these are all necessary to fix the Cirun builds :/ :

• Without unconditionally running gha-setup-vsdevenv, we can't find CMake
• Without inlining CMAKE_ANDROID_NDK, $NDKPATH is not expanded from matrix.extra_flags and CMake configure fails.
• Without switching to nttdl/setup-ndk I'll need to duplicate the powershell code to download the NDK before each cmake configure (Cirun images don't have the NDK)

But, as you mentioned above, I could put the non-powershell, Android -specific CMake defines back until a later PR if you'd like.

[compnerd]

I don't think I understand what you are suggesting. I don't see why you would not be able to extract just the installation of the NDK into a separate change that can go in first - that should have no impact on the GHA builds.

Separately, changing gha-setup-devenv could go in a separate change with no impact on GHA builders but further prepare the rules for supporting additional runners.

At that point, you could make just the changes needed to pass the extra require flags.

[compnerd]

This still conflates 2-3 different changes, but I suppose it is fine. The ninja changes are one item, the NDK installation and use are a separate item, and the PIC code is a third item. Please split changes into distinct issues being addressed in the future.

[kendalharland]

I suppose that's true. Given how GitHub doesn't make it easy to stack PRs, it's just harder to test as 3 separate PRs. But you're correct, those individual changes would independently work on top of the existing GH runners. Will do in the future.