Prefix perror(3) messages with program name.

It make it easier while debugging to know who is reporting the error:
Ninja itself or one of the command called by Ninja during the build
process or one of the generator which called Ninja.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/subprocess.cc b/src/subprocess.cc
index 1043e65..cef0ad3 100644
--- a/src/subprocess.cc
+++ b/src/subprocess.cc
@@ -157,7 +157,7 @@ void SubprocessSet::DoWork() {
   int ret = poll(fds.data(), fds.size(), -1);
   if (ret == -1) {
     if (errno != EINTR)
-      perror("poll");
+      perror("ninja: poll");
     return;
   }