Remove linker warning when getpid() is including.

When getpid() was recently added to the NaCl port it
mistakenly included a stub_warning() which causes any
programs that reference it to produce a linker warning.

BUG= http://code.google.com/p/nativeclient/issues/detail?id=2488
R=mseaborn@chromium.org

Review URL: https://codereview.chromium.org/23293002
1 file changed