posix: better launchapp error message

base/process_util_posix.cc

Index: base/process_util_posix.cc
diff --git a/base/process_util_posix.cc b/base/process_util_posix.cc
index 425f455d8a6f8ed27baa4d32fd738943f524ac95..45efe8bdcbd0ec29a057b716c0c6692ff9911948 100644
--- a/base/process_util_posix.cc
+++ b/base/process_util_posix.cc
@@ -274,8 +274,8 @@ bool LaunchApp(const std::vector<std::string>& argv,
       argv_cstr[i] = const_cast<char*>(argv[i].c_str());
     argv_cstr[argv.size()] = NULL;
     execvp(argv_cstr[0], argv_cstr.get());
-    LOG(ERROR) << "LaunchApp: exec failed!, argv_cstr[0] " << argv_cstr[0]
-        << ", errno " << errno;
+    LOG(ERROR) << "LaunchApp: execvp(" << argv_cstr[0] << ") failed: "
+               << strerror(errno);
     _exit(127);
   } else {
     // Parent process