Use larger write sizes for MCFillFragment.

This brings the pr26208 testcase down to 3.2 seconds. Not checking it in
since it does create a 4GB .o file.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@258149 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed