Check if the locally installed Android NDK matches the wanted NDK version

We were never actually checking `android_ndk_versions` if ANDROID_NDK_HOME was set,
as that environment variable always will be on the github runners.

Author: finagolfin

.github/workflows/scripts/install-and-build-with-sdk.sh

@@ -653,13 +653,14 @@ install_android_sdk() {
     # guess some common places where the swift-sdks file lives
     cd ~/Library/org.swift.swiftpm || cd ~/.config/swiftpm || cd ~/.local/swiftpm || cd ~/.swiftpm || cd /root/.swiftpm
 
+    # permit the "--android-ndk" flag to override the default
+    local android_ndk_version="${ANDROID_NDK_VERSION:-r27d}"
+
     # Download and install the Android NDK.
     # Note that we could use the system package manager, but it is
     # named different things for different distributions
     # (e.g., "google-android-ndk-r26-installer" on Debian)
-    if [[ ! -d "${ANDROID_NDK_HOME:-}" ]]; then
-        # permit the "--android-ndk" flag to override the default
-        local android_ndk_version="${ANDROID_NDK_VERSION:-r27d}"
+    if [[ ! -d "${ANDROID_NDK_HOME:-}" || ! $(grep "Pkg.ReleaseName = ${android_ndk_version}" "${ANDROID_NDK_HOME}/source.properties") ]]; then
         curl_with_retry -fsSL -o ndk.zip https://dl.google.com/android/repository/android-ndk-"${android_ndk_version}"-"$(uname -s)".zip
         command -v unzip >/dev/null || install_package unzip
         unzip -q ndk.zip