[XCOFF] Add functionality for parsing AIX XCOFF object file headers

Summary:
1. Add functionality for parsing AIX XCOFF object files headers.
2. Only support 32-bit AIX XCOFF object files in this patch.
3. Print out the AIX XCOFF object file header in YAML format.

Reviewers: sfertile, hubert.reinterpretcast, jasonliu, mstorsjo, zturner, rnk

Reviewed By: sfertile, hubert.reinterpretcast

Subscribers: jsji, mgorny, hiraditya, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59419

Patch by Digger Lin

llvm-svn: 357663
diff --git a/llvm/lib/Object/CMakeLists.txt b/llvm/lib/Object/CMakeLists.txt
index c9f7da9..242ae7e 100644
--- a/llvm/lib/Object/CMakeLists.txt
+++ b/llvm/lib/Object/CMakeLists.txt
@@ -23,6 +23,7 @@
   SymbolSize.cpp
   WasmObjectFile.cpp
   WindowsResource.cpp
+  XCOFFObjectFile.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Object