Add ADT headers to the cmake headers directory for LLVMSupport. NFC.

Xcode and MSVC list the headers and source files for each library.

LLVMSupport lists included the source files for ADT but not the headers.  This
add the ADT headers so that they are browsable by the UI.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279470 91177308-0d34-0410-b5e6-96231b3b80d8

Author: cooperp

lib/Support/CMakeLists.txt

@@ -130,6 +130,7 @@ add_llvm_library(LLVMSupport
   ADDITIONAL_HEADER_DIRS
   Unix
   Windows
+  ${LLVM_MAIN_INCLUDE_DIR}/llvm/ADT
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Support
 
   LINK_LIBS ${system_libs}