kiss: fix build-fail hook not causing exit

This wraps the call in a subshell so the die() call does not exit
the script early. Error code is also forced back to 0 so the
existing clean up code runs.

Closes #260

kiss

@@ -1007,7 +1007,7 @@ pkg_build() {
             # arg1: build-fail
             # arg2: package name
             # arg3: path to build directory
-            run_hook build-fail "$pkg" "$mak_dir/$1"
+            (run_hook build-fail "$pkg" "$mak_dir/$1") || :
 
             pkg_clean
             kill 0