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
1 file changed