Reland "[LLVM][llvm-objcopy] Added basic plumbing to get things started"

As discussed on llvm-dev I've implemented the first basic steps towards
llvm-objcopy/llvm-objtool (name pending).

This change adds the ability to copy (without modification) 64-bit
little endian ELF executables that have SHT_PROGBITS, SHT_NOBITS,
SHT_NULL and SHT_STRTAB sections.

Patch by Jake Ehrlich

Differential Revision: https://reviews.llvm.org/D33964

llvm-svn: 309043

test/CMakeLists.txt

@@ -61,6 +61,7 @@ set(LLVM_TEST_DEPENDS
           llvm-modextract
           llvm-mt
           llvm-nm
+          llvm-objcopy
           llvm-objdump
           llvm-opt-report
           llvm-pdbutil

tools/LLVMBuild.txt

@@ -40,6 +40,7 @@ subdirectories =
  llvm-modextract
  llvm-mt
  llvm-nm
+ llvm-objcopy
  llvm-objdump
  llvm-pdbutil
  llvm-profdata