Build the macOS app in one shared directory for incremental builds

mac/bundle.sh

@@ -1,11 +1,18 @@
 #!/bin/sh
 set -eu
 mac=$(cd "$(dirname "$0")" && pwd)
+root=$(dirname "$mac")
+shared=$HOME/Library/Caches/byre/build
 build=$mac/.build
 app=$build/byre.app
 svg=$mac/icon.svg
 icns=$build/byre.icns
-swift build --package-path "$mac" --configuration release
+mkdir -p "$shared" "$build"
+lockf -k "$shared.lock" sh -ec '
+rsync -rlc --delete --exclude /mac/.build "$1/mac" "$1/api" "$2/"
+swift build --package-path "$2/mac" --configuration release --no-color-diagnostics
+cp "$2/mac/.build/release/Byre" "$3"
+' sh "$root" "$shared" "$build/Byre"
 if [ ! "$icns" -nt "$svg" ]; then
 	iconset=$build/byre.iconset
 	rm -rf "$iconset"
@@ -18,7 +25,7 @@ if [ ! "$icns" -nt "$svg" ]; then
 fi
 rm -rf "$app"
 mkdir -p "$app/Contents/MacOS" "$app/Contents/Resources/fonts"
-cp "$build/release/Byre" "$app/Contents/MacOS/Byre"
+cp "$build/Byre" "$app/Contents/MacOS/Byre"
 cp "$mac/Info.plist" "$app/Contents/Info.plist"
 cp "$mac"/fonts/*.woff2 "$app/Contents/Resources/fonts/"
 cp "$icns" "$app/Contents/Resources/byre.icns"