Call normalize() in the common driver.

Previously only GNU driver calls InputGraph::normalize, but its
functionality is not and should not be limited to GNU ld. Other
driver should be able to use it.

Currently only linker scripts use the feature, so this change
won't change the existing behavior.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@208266 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Split LocallyImportedSymbolFile into two classes.

I have a plan to use VirtualArchiveFile in this file in the near future.
This change should improve the readability by itself, too.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@208365 91177308-0d34-0410-b5e6-96231b3b80d8
temporary commit.