COFF: Call exit(0) on success to not call destructors.
COFF: Call exit(0) on success to not call destructors.

This change cut the link time of chrome.dll from 24 seconds
to 22 seconds (5% gain). When the control reaches end of link(),
all output files have already been written. All in-memory
objects can just vanish. There is no use to call their dtors.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@241320 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld