MC: mark COFF .drectve section as REMOVE

The .drectve section should be marked as IMAGE_SCN_LNK_REMOVE.  This matches what
the MSVC toolchain does and accurately reflects that this section should not be
emitted into the final binary.  This section is merely information for the
linker, comprising of additional linker directives.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209273 91177308-0d34-0410-b5e6-96231b3b80d8