Build system: Fix Local Build Script for android.

Change the name of the `GITHUB_WORKSPACE` environment variable in the
android build script to `OUTPUT_DIR`, which is more intuitive when the
script is used for local builds.
Also test if the variable is defined before attempting to use it as the
target of the build output.

Signed-off-by: Michael Keller <github@ike.ch>

.github/workflows/android.yml

@@ -55,7 +55,7 @@ jobs:
         apt-get install --reinstall cpp-7 gcc-7-base libgcc-7-dev libcc1-0 gcc-7
         git config --global --add safe.directory ${SUBSURFACE_REPO_PATH}
         git config --global --add safe.directory ${SUBSURFACE_REPO_PATH}/libdivecomputer
-        bash -x ./subsurface/packaging/android/qmake-build.sh
+        OUTPUT_DIR=$GITHUB_WORKSPACE bash -x ./subsurface/packaging/android/qmake-build.sh
 
     - name: create version number
       id: version_number

packaging/android/qmake-build.sh

@@ -404,4 +404,7 @@ fi
 
 # now build the Subsurface aab
 make apk
-mv $(find . -name Subsurface-mobile.apk) "$GITHUB_WORKSPACE"/Subsurface-mobile-"$CANONICALVERSION".apk
+
+if [ -n "${OUTPUT_DIR+X}" ] ; then
+	mv $(find . -name Subsurface-mobile.apk) "$OUTPUT_DIR"/Subsurface-mobile-"$CANONICALVERSION".apk
+fi