Recommit r294464 "[ELF] - Added partial support for --emit-relocs (no...

Recommit r294464 "[ELF] - Added partial support for --emit-relocs (no --gc-section case, no /DISCARD/ support) #3"

with temporarily file name fix in testcase.

Original commit message:

-q, --emit-relocs - Generate relocations in output

Simplest implementation: 
* no GC case, 
* no "/DISCARD/" linkerscript command support.

This patch is extracted from D28612 / D29636,

Relative to PR31579.

Differential revision: https://reviews.llvm.org/D29663

llvm-svn: 294469