Fix two problems in the ExecuteBinary function.

- If the process exits abnormally then we will leak the stdout and
  stderr FDs. Fix it by closing the FDs before returning.

- If another child process exits then we will incorrectly return the
  result from that process instead of waiting for our child. Fix it
  by using waitpid instead of wait.

Change-Id: I8974d5e4bd33f264cd2d364f55a60f1f5cb7eb1a

libs/androidfw/PosixUtils.cpp

@@ -72,7 +72,8 @@ std::unique_ptr<ProcResult> ExecuteBinary(const std::vector<std::string>& argv)
     argv0[i] = argv[i].c_str();
   }
   argv0[argv.size()] = nullptr;
-  switch (fork()) {
+  int pid = fork();
+  switch (pid) {
     case -1: // error
       free(argv0);
       PLOG(ERROR) << "fork";
@@ -104,8 +105,10 @@ std::unique_ptr<ProcResult> ExecuteBinary(const std::vector<std::string>& argv)
       close(stdout[1]);
       close(stderr[1]);
       int status;
-      wait(&status);
+      waitpid(pid, &status, 0);
       if (!WIFEXITED(status)) {
+          close(stdout[0]);
+          close(stderr[0]);
           return nullptr;
       }
       std::unique_ptr<ProcResult> result(new ProcResult());