run-command.c: fix build warnings on Ubuntu
run-command.c: fix build warnings on Ubuntu

Building git on Ubuntu 9.10 warns that the return value of write(2)
isn't checked. These warnings were introduced in commits:

  2b541bf8 ("start_command: detect execvp failures early")
  a5487ddf ("start_command: report child process setup errors to the
parent's stderr")

GCC details:

  $ gcc --version
  gcc (Ubuntu 4.4.1-4ubuntu9) 4.4.1

Silence the warnings by reading (but not making use of) the return value
of write(2).

Signed-off-by: Michael Wookey <38cb29caf81650782db36db4f79a78cb2a683867@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git