ELF: Use a vector of pairs to sort sections ordered using --symbol-ordering-file.
ELF: Use a vector of pairs to sort sections ordered using --symbol-ordering-file.

This improved performance by 0.5-1% linking Chromium for Android.

Differential Revision: https://reviews.llvm.org/D45222

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@329106 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld