adds llvm build support incl. conan

CMakeLists.txt

@@ -15,11 +15,11 @@ if(TARGET tcc::tcc)
 endif()
 
 if(WITH_LLVM)
-	if(FALSE)
     if(DEFINED ENV{LLVM_HOME})
         find_path (LLVM_DIR LLVM-Config.cmake $ENV{LLVM_HOME}/lib/cmake/llvm)
     endif(DEFINED ENV{LLVM_HOME})
-	    find_package(LLVM REQUIRED CONFIG)
+    find_package(LLVM QUIET CONFIG)
+    if(LLVM_FOUND)
     	message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
     	message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
     	llvm_map_components_to_libnames(llvm_libs support core mcjit x86codegen x86asmparser)