[CMake] Properly conditionalize installation of lld libraries

[davezarzycki]

Summary

In what appears to be a copy-and-paste error, lld currently only install libraries if the lld tools are configured to build.

Instead, lld should allow the libraries to be installed even if if the lld tools are not being built. Additionally, if users want to only install the tools and not the libraries, the LLVM way of doing that is by checking for follow LLVM_INSTALL_TOOLCHAIN_ONLY.

This fixes PR35960.

[labath]

Yea, I probably just copied this from the add_lld_tool function without thinking whether it was correct. Anyway, thanks for fixing this.

cmake/modules/AddLLD.cmake

 macro(add_lld_library name)
   cmake_parse_arguments(ARG
     "SHARED"
     ""
     ""
     ${ARGN})
   if(ARG_SHARED)
     set(ARG_ENABLE_SHARED SHARED)
   endif()
   llvm_add_library(${name} ${ARG_ENABLE_SHARED} ${ARG_UNPARSED_ARGUMENTS})
   set_target_properties(${name} PROPERTIES FOLDER "lld libraries")
 
-  if (LLD_BUILD_TOOLS)
+  if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
     if(${name} IN_LIST LLVM_DISTRIBUTION_COMPONENTS OR
         NOT LLVM_DISTRIBUTION_COMPONENTS)
       set(export_to_lldtargets EXPORT lldTargets)
       set_property(GLOBAL PROPERTY LLD_HAS_EXPORTS True)
     endif()
 
     install(TARGETS ${name}
       COMPONENT ${name}