Small buildjni= fixes

fdroidserver/build.py

@@ -815,7 +815,7 @@ def build_local(app, thisbuild, vcs, build_dir, output_dir, srclib_dir, extlib_d
         nativecode = nativecode.strip()
         nativecode = None if not nativecode else nativecode
 
-    if thisbuild['buildjni'] != 'no':
+    if thisbuild['buildjni'] and thisbuild['buildjni'] != ['no']:
         if nativecode is not None:
             raise BuildException("Native code should have been built but none was packaged")
     if thisbuild['novcheck']:

fdroidserver/common.py

@@ -1456,7 +1456,7 @@ def scan_source(build_dir, root_dir, thisbuild):
     # buildjni=no to bypass this check)
     if (os.path.exists(os.path.join(root_dir, 'jni')) and
             not thisbuild['buildjni']):
-        logging.error('Found jni directory, but buildjni is not enabled')
+        logging.error('Found jni directory, but buildjni is not enabled. Set it to \'no\' to ignore.')
         count += 1
 
     return count