This patch is extracted from D96035, it adds support for the existing
DWARFLinker functionality. What is not supported yet:
1. Types deduplication(--odr mode).
2. Modules deduplication.
3. Generation of index tables.
Reland2: temporarily disabled call to "--linker llvm" for tls-variable.test
and location-expression.test as it does not work properly on bigendian
architecture.
Differential Revision: https://reviews.llvm.org/D153268
5f2a7fa67e