Fix the Android CI workflow by adding a post-install step the configure the SDK (#3424)

Fixes the Android CI workflow

### Motivation:

The recently-added Android SDK workflow
[fails](https://github.com/apple/swift-nio/actions/runs/18718487605/job/53384086329?pr=3418)
(as mentioned at
#3418 (comment)). The
confusing error message is due to a post-install step that is needed to
download and link the Android NDK into the Swift SDK's artifactbundle.

This PR also adds a one-line fix to
[Sources/NIOPerformanceTester/main.swift](main...swift-android-sdk:swift-nio:main#diff-de179adbbfacb89c9533f4efd21f7f641eedc0c8642d7d650cdfc9d9278a7a55)
that gets it building for Android so the entire swift-nio package can be
built.

### Modifications:

Adds a post-install step to the SDK installation that is needed for the
Swift SDK for Android. This is the same technique used by
swiftlang/github-workflows#172, and is described
as a necessary step in the [Android getting started
guide](https://github.com/swiftlang/swift-org-website/blob/0dc655ce267e7b6bada2a2032cc7855c3b5e19d9/documentation/articles/swift-android-getting-started.md)

### Result:

The "Android Swift SDK" CI check should now pass successfully. See an
example at
https://github.com/swift-android-sdk/swift-nio/actions/runs/18761057590/job/53525442382

### Note:

This PR will _not_ pass the Android check until it has been merged,
because it relies on being able to down the the script
https://raw.githubusercontent.com/apple/swift-nio/main/scripts/install_swift_sdk.sh
from `apple/swift-nio/main`, which will not include the Android fix
until the PR is merged. But once it is merged, the Android SDK CI should
start passing.

Author: marcprux

.github/workflows/main.yml

@@ -75,8 +75,6 @@ jobs:
     name: Android Swift SDK
     # Workaround https://github.com/nektos/act/issues/1875
     uses: apple/swift-nio/.github/workflows/android_sdk.yml@main
-    with:
-      additional_command_arguments: "--target NIOCore"
 
   macos-tests:
     name: macOS tests

.github/workflows/pull_request.yml

@@ -109,8 +109,6 @@ jobs:
     name: Android Swift SDK
     # Workaround https://github.com/nektos/act/issues/1875
     uses: apple/swift-nio/.github/workflows/android_sdk.yml@main
-    with:
-      additional_command_arguments: "--target NIOCore"
 
   release-builds:
     name: Release builds

Sources/NIOPerformanceTester/main.swift

@@ -28,7 +28,12 @@ import NIOCore
 import NIOEmbedded
 import NIOFoundationCompat
 import NIOHTTP1
+#if os(Android)
+// workaround for error: reference to var 'stdout' is not concurrency-safe because it involves shared mutable state
+@preconcurrency import NIOPosix
+#else
 import NIOPosix
+#endif
 import NIOWebSocket
 
 // Use unbuffered stdout to help detect exactly which test was running in the event of a crash.

scripts/install_swift_sdk.sh

@@ -25,6 +25,7 @@ version="${INSTALL_SWIFT_VERSION:=""}"
 arch="${INSTALL_SWIFT_ARCH:="aarch64"}"
 os_image="${INSTALL_SWIFT_OS_IMAGE:="ubuntu22.04"}"
 sdk="${INSTALL_SWIFT_SDK:="static-sdk"}"
+android_ndk_version="${INSTALL_ANDROID_NDK:="r27d"}"
 
 if [[ ! ( -n "$branch" && -z "$version" ) && ! ( -z "$branch" && -n "$version") ]]; then
   fatal "Exactly one of build or version must be defined."
@@ -127,3 +128,20 @@ swift --version
 
 log "Installing Swift SDK"
 swift sdk install "$sdk_path"
+
+log "Swift SDK Post-install"
+if [[ "$sdk" == "android-sdk" ]]; then
+    # guess some common places where the swift-sdks folder lives
+    cd ~/Library/org.swift.swiftpm || cd ~/.config/swiftpm || cd ~/.local/swiftpm || cd ~/.swiftpm || cd /root/.swiftpm || fatal "Cannot locate swiftpm config directory"
+
+    # download and link the NDK
+    android_ndk_url="https://dl.google.com/android/repository/android-ndk-${android_ndk_version}-$(uname -s).zip"
+    log "Android Native Development Kit URL: ${android_ndk_url}"
+    "$CURL_BIN" -fsSL -o ndk.zip --retry 3 "${android_ndk_url}"
+    unzip -q ndk.zip
+    rm ndk.zip
+    export ANDROID_NDK_HOME="${PWD}/android-ndk-${android_ndk_version}"
+    bundledir=$(find . -type d -maxdepth 2 -name '*android*.artifactbundle' | head -n 1)
+    "${bundledir}"/swift-android/scripts/setup-android-sdk.sh
+    cd - || fatal "Cannot cd back to previous directory"
+fi