[elflib] Trim whitespace from the end of filenames in ids.txt

We hit an issue where a space at the end of a filename caused a
fatal error. This is not really the sort of thing that should
be causing symbolizer to fail at all but this is good duct tape
to solve the problem. It's probably good to do this anyway as it
increases the number of cases in which we can successfully symbolize.

Change-Id: Ie6f2e576ecb10cf53b460a23cc0489c821ed2129
diff --git a/elflib/elflib.go b/elflib/elflib.go
index c4fa94d..f4c1aaa 100644
--- a/elflib/elflib.go
+++ b/elflib/elflib.go
@@ -156,8 +156,8 @@
 		if len(parts) != 2 {
 			return nil, fmt.Errorf("error parsing on line %d: found `%s`", line, text)
 		}
-		build := parts[0]
-		filename := parts[1]
+		build := strings.TrimSpace(parts[0])
+		filename := strings.TrimSpace(parts[1])
 		out = append(out, BinaryFileRef{Filepath: filename, BuildID: build})
 	}
 	return out, nil