[CMake] Separate LLVM_ENABLE_LTO and LLVM_ENABLE_LLD

[phosek]

Summary

These two are options independent: it's possible to use LLD without LTO, and it's possible to do LTO build without LLD.

[beanz]

Many thanks for the quick cleanup! LGTM!

[mehdi_amini]

Yes, thanks!

cfe/trunk/CMakeLists.txt

if(BOOTSTRAP_LLVM_BUILD_INSTRUMENTED)
     set(NEXT_CLANG_STAGE ${NEXT_CLANG_STAGE}-instrumented)
   endif()
   message(STATUS "Setting next clang stage to: ${NEXT_CLANG_STAGE}")
   
   
   set(STAMP_DIR ${CMAKE_CURRENT_BINARY_DIR}/${NEXT_CLANG_STAGE}-stamps/)
   set(BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/${NEXT_CLANG_STAGE}-bins/)
 
+  if(BOOTSTRAP_LLVM_ENABLE_LLD)
+    add_dependencies(clang-bootstrap-deps lld)
+  endif()
+
   # If the next stage is LTO we need to depend on LTO and possibly lld or LLVMgold
   if(BOOTSTRAP_LLVM_ENABLE_LTO OR LLVM_ENABLE_LTO AND NOT LLVM_BUILD_INSTRUMENTED)
     if(APPLE)
       add_dependencies(clang-bootstrap-deps LTO)
       # on Darwin we need to set DARWIN_LTO_LIBRARY so that -flto will work
       # using the just-built compiler, and we need to override DYLD_LIBRARY_PATH
       # so that the host object file tools will use the just-built libLTO.
       # However if System Integrity Protection is enabled the DYLD variables
       # will be scrubbed from the environment of any base system commands. This
       # includes /bin/sh, which ninja uses when executing build commands. To
       # work around the envar being filtered away we pass it in as a CMake
       # variable, and have LLVM's CMake append the envar to the archiver calls.
       set(LTO_LIBRARY -DDARWIN_LTO_LIBRARY=${LLVM_SHLIB_OUTPUT_INTDIR}/libLTO.dylib
         -DDYLD_LIBRARY_PATH=${LLVM_LIBRARY_OUTPUT_INTDIR})
     elseif(NOT WIN32)
       add_dependencies(clang-bootstrap-deps llvm-ar llvm-ranlib)
-      if(BOOTSTRAP_LLVM_ENABLE_LLD)
-        add_dependencies(clang-bootstrap-deps lld)
-      elseif(LLVM_BINUTILS_INCDIR)
+      if(NOT BOOTSTRAP_LLVM_ENABLE_LLD AND LLVM_BINUTILS_INCDIR)
         add_dependencies(clang-bootstrap-deps LLVMgold)
       endif()
       set(LTO_AR -DCMAKE_AR=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-ar)
       set(LTO_RANLIB -DCMAKE_RANLIB=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-ranlib)
     endif()
   endif()
 
   add_custom_target(${NEXT_CLANG_STAGE}-clear