contrib: Add requested changes to build-flatpak.sh

- Add the flathub.org remote if it doesn't exist
- Download required SDK and runtimes if not downloaded
- Display the path of the created bundle with the command to install it

contrib/build-flatpak.sh

@@ -3,13 +3,28 @@ export LC_ALL=C
 set -e
 SECONDS=0
 
-repo_root="$(realpath "$(dirname "$0")/..")"
-mkdir -p "$repo_root/build"
-cd "$repo_root/build"
+gc_platform="org.kde.Platform//5.15-23.08"
+gc_sdk="org.kde.Sdk//5.15-23.08"
+gc_id="us.gridcoin.Gridcoin-Research"
+gc_output_file="Gridcoin-Research.flatpak"
+gc_repo_root="$(realpath "$(dirname "$0")/..")"
+gc_builddir="$gc_repo_root/build"
 
-echo "$repo_root"
-flatpak-builder flatpak-build "$repo_root/contrib/flatpak-manifest.json" --force-clean
-flatpak build-export gridcoin-flatpak flatpak-build
-flatpak build-bundle gridcoin-flatpak Gridcoin-Research.flatpak us.gridcoin.Gridcoin-Research
+# Add the required flathub.org repo to the list of local repos, if it wasn't added earlier.
+flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
 
-echo "Took $SECONDS seconds to build the Flatpak bundle."
+# Check if the required SDK and runtime are installed. If not, install them.
+flatpak info "$gc_platform" &>/dev/null || flatpak install --noninteractive -y flathub "$gc_platform"
+flatpak info "$gc_sdk" &>/dev/null || flatpak install --noninteractive -y flathub "$gc_sdk"
+
+echo "Started building the Gridcoin-Research Flatpak bundle..."
+mkdir -p "$gc_builddir"
+flatpak-builder --state-dir="$gc_builddir/flatpak-cache" "$gc_builddir/flatpak-build" "$gc_repo_root/contrib/flatpak-manifest.json" --force-clean
+flatpak build-export "$gc_builddir/gridcoin-flatpak" "$gc_builddir/flatpak-build"
+flatpak build-bundle "$gc_builddir/gridcoin-flatpak" "$gc_builddir/$gc_output_file" "$gc_id"
+
+relative_output="$(realpath --relative-to="$PWD" "$gc_builddir/$gc_output_file")"
+echo ""
+echo "Took $SECONDS seconds to build the Flatpak bundle. You can find the output in $relative_output"
+echo "To install it, run the command below:"
+echo "flatpak install $relative_output"