Scripts: Add -only-download option to Linux deps

scripts/deps/build-dependencies-linux.sh

@@ -6,7 +6,7 @@
 set -e
 
 if [ "$#" -lt 1 ]; then
-    echo "Syntax: $0 [-system-freetype] [-system-harfbuzz] [-system-libjpeg] [-system-libpng] [-system-libwebp] [-system-libzip] [-system-zstd] [-system-qt] [-skip-download] [-skip-cleanup] <output directory>"
+    echo "Syntax: $0 [-system-freetype] [-system-harfbuzz] [-system-libjpeg] [-system-libpng] [-system-libwebp] [-system-libzip] [-system-zstd] [-system-qt] [-skip-download] [-skip-cleanup] [-only-download] <output directory>"
     exit 1
 fi
 
@@ -51,6 +51,10 @@ for arg in "$@"; do
 		echo "Not removing build directory."
 		SKIP_CLEANUP=true
 		shift
+	elif [ "$arg" == "-only-download" ]; then
+		echo "Only downloading sources."
+		ONLY_DOWNLOAD=true
+		shift
 	fi
 done
 
@@ -188,6 +192,11 @@ if [ "$SKIP_DOWNLOAD" != true ]; then
 	fi
 fi
 
+# Only downloading sources?
+if [ "$ONLY_DOWNLOAD" == true ]; then
+	exit 0
+fi
+
 echo "Building libbacktrace..."
 rm -fr "libbacktrace-$LIBBACKTRACE"
 tar xf "$LIBBACKTRACE.tar.gz"