Add basic zlib support to LLVM. This would allow to use compression/uncompression in selected LLVM tools.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180083 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c8c3038..d15a54b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -124,6 +124,8 @@
 
 option(LLVM_ENABLE_THREADS "Use threads if available." ON)
 
+option(LLVM_ENABLE_ZLIB "Use zlib for compression/decompression if available." ON)
+
 if( LLVM_TARGETS_TO_BUILD STREQUAL "all" )
   set( LLVM_TARGETS_TO_BUILD ${LLVM_ALL_TARGETS} )
 endif()