Merge pull request #2440 from jdrouhard/dry-run-fix

fix: don't attempt to write and stat the lock file during dry runs
diff --git a/src/build.cc b/src/build.cc
index 6587d1b..fca119c 100644
--- a/src/build.cc
+++ b/src/build.cc
@@ -846,7 +846,7 @@
 
   status_->BuildEdgeStarted(edge, start_time_millis);
 
-  TimeStamp build_start = -1;
+  TimeStamp build_start = config_.dry_run ? 0 : -1;
 
   // Create directories necessary for outputs and remember the current
   // filesystem mtime to record later