Parallelize build jobs according to CPU count

contrib/coverage.bash

@@ -1,17 +1,55 @@
 #!/usr/bin/env bash
 set -e
 
+usage() {
+	cat <<"EOF"
+Generates LCOV code coverage report for RGBDS.
+Options:
+    -h, --help     show this help message
+    -o, --open     open the HTML report in the preferred application
+    --jobs <n>     build RGBDS and external codebases with `make -j<n>`
+    --os <os>      skip tests known to fail on <os> (e.g. `macos-14`)
+EOF
+}
+
+# Parse options in pure Bash because macOS `getopt` is stuck
+# in what util-linux `getopt` calls `GETOPT_COMPATIBLE` mode
+make_args=()
+runtests_args=()
+open_report=false
+while [[ $# -gt 0 ]]; do
+	case "$1" in
+		-h|--help)
+			usage
+			exit 0
+			;;
+		-o|--open)
+			open_report=true
+			;;
+		--jobs)
+			shift
+			make_args+=("-j" "$1")
+			runtests_args+=("--jobs" "$1")
+			;;
+		--os)
+			shift
+			runtests_args+=("--os" "$1")
+			;;
+		*)
+			echo "$(basename "$0"): unknown option '$1'"
+			exit 1
+			;;
+	esac
+	shift
+done
+
 # Build RGBDS with gcov support
-make coverage -j
+make coverage "${make_args[@]}"
 
 # Run the tests
 pushd test
 external/fetch-repos.sh
-if [[ $# -eq 0 ]]; then
-  ./run-tests.sh
-else
-  ./run-tests.sh --os "$1"
-fi
+./run-tests.sh "${runtests_args[@]}"
 popd
 
 # Generate coverage logs
@@ -24,12 +62,14 @@ lcov -c --no-external -d . -o "$COVERAGE_INFO"
 lcov -r "$COVERAGE_INFO" src/asm/parser.{hpp,cpp} src/link/script.{hpp,cpp} -o "$COVERAGE_INFO"
 genhtml --dark-mode --num-spaces 4 -f -s -o coverage/ "$COVERAGE_INFO"
 
-# Check whether running from coverage.yml workflow
-if [ "$1" != "ubuntu-ci" ]; then
-  # Open report in web browser
-  if [ "$(uname)" == "Darwin" ]; then
-    open coverage/index.html
-  else
-    xdg-open coverage/index.html
-  fi
+if "$open_report"; then
+	# Open the report in the preferred web browser
+	if [ "$(uname)" == "Darwin" ]; then
+		open coverage/index.html
+	else
+		xdg-open coverage/index.html
+	fi
+else
+	# Output the path to the report
+	echo "Generated LCOV report at $PWD/coverage/index.html"
 fi