[flang][cmake] Separate FLANG_INCLUDE_TOOLS from FLANG_BUILD_TOOLS (#145005)

If we disable `FLANG_BUILD_TOOLS`, not only building the tools but also
generating the targets for them is skipped now. On the other hand, llvm
separates them into `LLVM_BUILD_TOOLS` and `LLVM_INCLUDE_TOOLS`.
This patch introduces `FLANG_INCLUDE_TOOLS` for the distinction.

Author: parabola94

flang/CMakeLists.txt

@@ -504,9 +504,10 @@ add_subdirectory(include)
 add_subdirectory(lib)
 add_subdirectory(cmake/modules)
 
+option(FLANG_INCLUDE_TOOLS "Generate build targets for the Flang tools." ON)
 option(FLANG_BUILD_TOOLS
   "Build the Flang tools. If OFF, just generate build targets." ON)
-if (FLANG_BUILD_TOOLS)
+if (FLANG_INCLUDE_TOOLS)
   add_subdirectory(tools)
 endif()