Fixed "${folder^}Activity: bad substitution" with bash 3.2 on macOS

(cherry picked from commit c36f773eb47693ad360dd3c97c347e9ab07cfa4c)

build-scripts/androidbuild.sh

@@ -81,7 +81,7 @@ do
 done
 
 # Uppercase the first char in the activity class name because it's Java
-ACTIVITY="${folder^}Activity"
+ACTIVITY="$(echo $folder | awk '{$1=toupper(substr($1,0,1))substr($1,2)}1')Activity"
 sed -i -e "s|\"SDLActivity\"|\"$ACTIVITY\"|g" $BUILDPATH/app/src/main/AndroidManifest.xml
 
 # Fill in a default Activity