[infer][java] Checks if the output jar exists on disk before trying to load the analysis artifacts from it

Summary:
During the incremental analysis using the Buck distributed cache, if there is a cache hit for a given module, the output jars for the intermediate targets are not necessarily dowloaded. We therefore need to filter the jar files that are present on disk before loading the analysis artifacts from it.

This will also be neccesary when combined with the --keep-going option of Buck

Reviewed By: sblackshear

Differential Revision: D3941853

fbshipit-source-id: befda63

infer/lib/python/inferlib/bucklib.py

@@ -279,7 +279,8 @@ def get_output_jars(targets):
     else:
         audit_output = subprocess.check_output(
             ['buck', 'audit', 'classpath'] + targets)
-        return audit_output.strip().split('\n')
+        classpath_jars = audit_output.strip().split('\n')
+        return filter(os.path.isfile, classpath_jars)
 
 
 def collect_results(args, start_time, targets):