feat(compdb): print out command for failed extractions (#4546)

Bug: 151096875
Test: run prebuilts/build-tools/build-prebuilts.sh
Change-Id: I541d48b8622b6439ff57e88f2ee1ece255bb39ae
diff --git a/kythe/go/extractors/config/runextractor/compdb/compdb.go b/kythe/go/extractors/config/runextractor/compdb/compdb.go
index cd91729..051077a 100644
--- a/kythe/go/extractors/config/runextractor/compdb/compdb.go
+++ b/kythe/go/extractors/config/runextractor/compdb/compdb.go
@@ -72,7 +72,7 @@
 			if err := extractOne(ctx, extractor, entry, env); err != nil {
 				// Log error, but continue processing other compilations.
 				atomic.AddUint64(&failCount, 1)
-				log.Printf("Error extracting compilation: %v", err)
+				log.Printf("Error extracting compilation with command '%s': %v", entry.Command, err)
 			}
 		}(entry)
 	}