iOS: adjust GitHub Action to new build format

It's frustrating that I can't get the translation.qrc support the translation
files to be created in the build directory. Having them as part of the sources
just feels wrong.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

.github/workflows/ios.yml

@@ -25,11 +25,8 @@ jobs:
         xzcat Qt-5.14.1-ios.tar.xz | tar -x -C $HOME/Qt -f -
     - name: build Subsurface-mobile for iOS
       run: |
-        cd packaging/ios
+        mkdir -p $HOME/build
+        cd $HOME/build
         ln -s $HOME/Qt Qt
-        echo "build dependencies"
-        bash -x build.sh -simulator
-        echo "Subsurface-mobile for iOS"
-        cd build-Subsurface-mobile-*for_iOS-Release
-        sed -i.bak 's/-Wall/-Wno-everything/' Makefile # make the build far less verbose
-        make -j2
+        echo "build for simulator"
+        bash -x $GITHUB_WORKSPACE/packaging/ios/build.sh -simulator