Add -Wextra warning flag.

Fix triggered warnings:
- unused parameter
- type qualifiers ignored on function return type
- missing initializer for member

1 files changed, 1 insertions, 1 deletions

diff --git a/src/build.cc b/src/build.cc
index 9465532..332a70f 100644
--- a/src/build.cc
+++ b/src/build.cc
@@ -419,7 +419,7 @@ struct DryRunCommandRunner : public CommandRunner {
     finished_.push(edge);
     return true;
   }
-  virtual Edge* WaitForCommand(bool* success, string* output) {
+  virtual Edge* WaitForCommand(bool* success, string* /* output */) {
     if (finished_.empty())
       return NULL;
     *success = true;