[cmake] Don't set install rules for tblgen if building utils is disabled

[loladiro]

Summary

This is a follow up to D64032. Afterwards if building utils is disabled
and cross compilation is attempted, CMake will complain that adding
install() directives to targets with EXCLUDE_FROM_ALL set is "undefined".
Indeed, it appears depending on the CMake version and the selected
Generator, the install rule will error because the underlying target isn't
built. Fix that by not adding the install rule if building utils is not
requested. Note that this doesn't prevent building tblgen as a
dependency in not cross-build, even if building tools is disabled.

[smeenai]

LGTM

llvm/cmake/modules/TableGen.cmake

if( ${${project}_TABLEGEN} STREQUAL "${target}" )
       # If we're using the host tablegen, and utils were not requested, we have no
       # need to build this tablegen.
       if ( NOT LLVM_BUILD_UTILS )
         set_target_properties(${target} PROPERTIES EXCLUDE_FROM_ALL ON)
       endif()
     endif()
   endif()
 
-  if (${project} STREQUAL LLVM AND NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
+  if (${project} STREQUAL LLVM AND NOT LLVM_INSTALL_TOOLCHAIN_ONLY AND LLVM_BUILD_UTILS)
     set(export_to_llvmexports)
     if(${target} IN_LIST LLVM_DISTRIBUTION_COMPONENTS OR
         NOT LLVM_DISTRIBUTION_COMPONENTS)
       set(export_to_llvmexports EXPORT LLVMExports)
     endif()
 
     install(TARGETS ${target}
             ${export_to_llvmexports}
             RUNTIME DESTINATION ${LLVM_TOOLS_INSTALL_DIR})
   endif()
   set_property(GLOBAL APPEND PROPERTY LLVM_EXPORTS ${target})
 endmacro()