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/parsers.cc b/src/parsers.cc
index b9c1190..4aeb73c 100644
--- a/src/parsers.cc
+++ b/src/parsers.cc
@@ -291,7 +291,7 @@ bool ManifestParser::Parse(const string& input, string* err) {
           // XXX remove this hack, or make it more principled.
           char cwd[1024];
           if (!getcwd(cwd, sizeof(cwd))) {
-            perror("getcwd");
+            perror("ninja: getcwd");
             return 1;
           }
           value = cwd + value.substr(9);