Drop the .llvm_addrsig section from rewritten objects

[MisterDA]

The address-significance table emitted by Clang holds symbol table indices, which become stale when flexlink rewrites an object's symbol table to add the relocation table. lld-link rejects objects with an invalid .llvm_addrsig section. The section is an optional hint for the linker's identical-code-folding pass and can safely be dropped.

It is also possible to tell Clang not to emit this section with -fno-addrsig.

Proper handling of this section could come later, for now it's easy to silently ignore it.

See also:

• https://llvm.org/docs/Extensions.html#sht-llvm-addrsig-section-address-significance-table
• https://clang.llvm.org/docs/UsersManual.html#cmdoption-faddrsig
• https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/36912.pdf