clean up more of llvm/runtimes/CMakeList.txt

Author: nickdesaulniers

llvm/CMakeLists.txt

@@ -186,13 +186,8 @@ if(LIBC_GPU_BUILD)
   list(APPEND RUNTIMES_amdgcn-amd-amdhsa_LLVM_ENABLE_RUNTIMES "libc")
 endif()
 
-set(NEED_LIBC_HDRGEN FALSE)
-if("libc" IN_LIST LLVM_ENABLE_RUNTIMES)
-  set(NEED_LIBC_HDRGEN TRUE)
-endif()
 foreach(_name ${LLVM_RUNTIME_TARGETS})
   if("libc" IN_LIST RUNTIMES_${_name}_LLVM_ENABLE_RUNTIMES)
-    set(NEED_LIBC_HDRGEN TRUE)
     if("${_name}" STREQUAL "amdgcn-amd-amdhsa" OR "${_name}" STREQUAL "nvptx64-nvidia-cuda")
       set(LLVM_LIBC_GPU_BUILD ON)
     endif()
@@ -202,26 +197,6 @@ if("${LIBC_TARGET_TRIPLE}" STREQUAL "amdgcn-amd-amdhsa" OR
    "${LIBC_TARGET_TRIPLE}" STREQUAL "nvptx64-nvidia-cuda")
   set(LLVM_LIBC_GPU_BUILD ON)
 endif()
-if(NEED_LIBC_HDRGEN)
-  # To build the libc runtime, we need to be able to build few libc build
-  # tools from the "libc" project. So, we add it to the list of enabled
-  # projects.
-  if (NOT "libc" IN_LIST LLVM_ENABLE_PROJECTS)
-    message(STATUS "Enabling libc project to build libc build tools")
-    list(APPEND LLVM_ENABLE_PROJECTS "libc")
-  endif()
-endif()
-
-foreach(proj IN LISTS LLVM_ENABLE_RUNTIMES)
-  if("${proj}" IN_LIST LLVM_ENABLE_PROJECTS)
-    # The 'libc' project bootstraps a few executables via the project build and
-    # should not emit an error currently.
-    if(NOT (NEED_LIBC_HDRGEN AND "${proj}" STREQUAL "libc"))
-      message(FATAL_ERROR "Runtime project \"${proj}\" found in LLVM_ENABLE_PROJECTS and LLVM_ENABLE_RUNTIMES. It must only appear in one of them and that one should almost always be LLVM_ENABLE_RUNTIMES.")
-    endif()
-  endif()
-endforeach()
-unset(NEED_LIBC_HDRGEN)
 
 # LLVM_ENABLE_PROJECTS_USED is `ON` if the user has ever used the
 # `LLVM_ENABLE_PROJECTS` CMake cache variable.  This exists for