fix syntax error for disabled function

scripts/common.sh

@@ -57,7 +57,8 @@ function build() {
 function test_install() {
     # TODO at the time of writing, this plainly fails with dependency errors
     #      also it cannot automatically work around multiple conflicting packages
-	#debi --with-depends
+    #debi --with-depends
+    :
 }
 
 function prepare_artifacts() {