[Writer][ELF] Use correct data types for sizes. Fixes integer overflow bug.

This only happens when the section header count is > 1024.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@176747 91177308-0d34-0410-b5e6-96231b3b80d8
Fix (possible) MSVC miscompile in debug mode.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@176748 91177308-0d34-0410-b5e6-96231b3b80d8
[Driver][GNU] Accept and ignore more options.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@176749 91177308-0d34-0410-b5e6-96231b3b80d8