fix(ci): let the Android build scripts respect a caller-set ANDROID_HOME

build-android.sh hardcoded `export ANDROID_HOME="$HOME/Android/Sdk"`,
which discarded whatever the caller had set. In the builder image the SDK
is at /opt/android-sdk and the job exports exactly that, so the script
looked for an NDK under /root/Android/Sdk, found nothing, and the build
died a minute in with "Android SDK not found" -- the first automatic
`latest` APK build failed on this and nothing else.

Now a default rather than an override, matching what
test-player-conformance.sh already did. NDK_HOME likewise prefers an
explicitly pinned ANDROID_NDK_HOME over guessing with `ls | head -1`,
which is how CI pins an exact NDK revision.

A missing SDK now fails immediately and says which variable to set,
instead of letting `ls` print its own error and the real failure surface
a minute later inside the tauri CLI.

android-dev.sh had the same override and gets the same treatment.

scripts/android-dev.sh

@@ -7,7 +7,7 @@ echo "======================================"
 # Setup environment
 echo "Setting up environment..."
 source "$HOME/.cargo/env.fish" 2>/dev/null || source "$HOME/.cargo/env" || true
-export ANDROID_HOME="$HOME/Android/Sdk"
+export ANDROID_HOME="${ANDROID_HOME:-$HOME/Android/Sdk}"
 export NDK_HOME="$ANDROID_HOME/ndk/$(ls $ANDROID_HOME/ndk 2>/dev/null | head -1)"
 
 # Check prerequisites

scripts/build-android.sh

@@ -6,9 +6,26 @@ set -e
 # Source Rust environment
 source "$HOME/.cargo/env.fish" 2>/dev/null || source "$HOME/.cargo/env" 2>/dev/null || true
 
-# Set Android environment variables
+# Set Android environment variables.
-export ANDROID_HOME="$HOME/Android/Sdk"
+#
-export NDK_HOME="$ANDROID_HOME/ndk/$(ls "$ANDROID_HOME/ndk" | head -1)"
+# Defaults, not overrides. A developer's SDK is at ~/Android/Sdk, but CI runs in
+# the builder image where it lives at /opt/android-sdk and the job sets
+# ANDROID_HOME accordingly — hardcoding the home-directory path here silently
+# discarded that and the build died with "Android SDK not found" a minute in.
+# `test-player-conformance.sh` already had this right; this script did not.
+export ANDROID_HOME="${ANDROID_HOME:-$HOME/Android/Sdk}"
+export ANDROID_SDK_ROOT="${ANDROID_SDK_ROOT:-$ANDROID_HOME}"
+
+if [ ! -d "$ANDROID_HOME/ndk" ]; then
+    echo "❌ No NDK directory at $ANDROID_HOME/ndk" >&2
+    echo "   Set ANDROID_HOME to your SDK location, or install the NDK." >&2
+    exit 1
+fi
+
+# Respect an NDK the caller has already picked (CI pins an exact revision via
+# ANDROID_NDK_HOME); otherwise take whatever is installed.
+export NDK_HOME="${NDK_HOME:-${ANDROID_NDK_HOME:-$ANDROID_HOME/ndk/$(ls "$ANDROID_HOME/ndk" | head -1)}}"
+export ANDROID_NDK_HOME="$NDK_HOME"
 
 echo "🤖 Building Android APK..."
 echo "Android SDK: $ANDROID_HOME"