Use prebuilt static-MUSL skip binary target on Android hosts

[hpr]

Problem

Package.swift selects the skip transpiler like this:

• #if os(macOS) → prebuilt macOS binary target
• #elseif os(Linux) → prebuilt static-MUSL skip-linux.zip binary target
• #else → build skipstone (+ SwiftSyntax) from source

Swift's compilation conditions treat Android as os(Android), not os(Linux), so on Android hosts (e.g. Termux/bionic) the manifest falls through to the #else branch and builds skipstone + SwiftSyntax 602 from source. That host build spikes 5–8 GB RSS in single swift-frontend processes, which OOM-kills typical Android devices.

Fix

Change the condition to #elseif os(Linux) || os(Android). The published static-MUSL skip binary itself runs fine on bionic (verified on-device, aarch64 Termux: skip version works via the binary target).

Companion PR

The published skip-linux.zip artifactbundle currently declares only *-unknown-linux-gnu in its info.json supportedTriples, so SwiftPM on an Android host still rejects the binary target ("Tool 'skip' is not supported on the target platform"). That list is generated by build_linux_plugin.sh at release time; skiptools/skipstone#266 adds the Android host triples (*-unknown-linux-android, *-unknown-linux-android24) so future releases work out of the box. (I verified the end-to-end flow by repacking the 1.9.5 skip-linux.zip with the Android triples added; swift build then picks the binary target and skipstone/SwiftSyntax leave the dependency graph entirely.)

Testing

This is a host-platform manifest condition, so there is no meaningful unit test for it (the repo's tests exercise the skip tool itself). Verified manually on-device (aarch64 Android/Termux, Swift 6.3.2 Android toolchain): with the condition fix + a triples-extended artifactbundle, swift build uses the prebuilt binary and no host SwiftSyntax build occurs.

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