[ELF] - Linkerscript: implement EXCLUDE_FILE in the middle of a input section description.

This is PR30387:

From PR description:
We fail to parse

SECTIONS
{
  foo :
  {
    *(sec0 EXCLUDE_FILE (zed1.o) sec1  EXCLUDE_FILE (zed2.o) sec2 )
  }
}
The semantics according to bfd are:

Include sec1 from every file but zed1.o
Include sec2 from every file but zed2.o
Include sec0 from every file

Patch implements the support.

Differential revision: https://reviews.llvm.org/D24650

llvm-svn: 281721