Don't refer to pthread_cancel in libgcc

This is a backport of upstream commit svn://gcc.gnu.org/svn/gcc/trunk@188400

BUG= http://code.google.com/p/nativeclient/issues/detail?id=2561
TEST= toolchain trybots

R=khim@google.com

Review URL: https://chromiumcodereview.appspot.com/10537138
2 files changed