default: only set default 'location' option if there's an install script

slapos/recipe/build/__init__.py

@@ -227,11 +227,6 @@ class Script(EnvironMixin):
     self.buildout = buildout
     self.name = name
     self.logger = logging.getLogger('SlapOS build of %s' % self.name)
-    try:
-      self.options['location'] = self.options['location'].strip()
-    except KeyError:
-      self.options['location'] = os.path.join(
-        buildout['buildout']['parts-directory'], self.name)
     missing = True
     keys = 'init', 'install', 'update'
     for option in keys:
@@ -247,17 +242,21 @@ class Script(EnvironMixin):
       self.keep_on_error = True
     else:
       self.keep_on_error = False
+    if self._install and 'location' not in options:
+      options['location'] = os.path.join(
+        buildout['buildout']['parts-directory'], self.name)
     EnvironMixin.__init__(self, False)
     if self._init:
       self._exec(self._init)
 
   def _exec(self, script):
     options = self.options
-    exec(script, dict(GLOBALS,
-      self=self,
-      options=options,
-      location=options['location'],
-    ))
+    g = dict(GLOBALS, self=self, options=options)
+    try:
+      g['location'] = options['location']
+    except KeyError:
+      pass
+    exec(script, g)
 
   def install(self):
     if not self._install: