backend/build: improve LLVM link options

Update options according to llvm-config:

* delete "--stdlib=libc++"  (it seems to provoke runtime link errors on Linux)
* remove "-lffi" (it doesn't seem to be required)
* remove "-lc++" on macOS

Also move Linux system libs options to llvm.def (as for macOS)

buildSrc/src/main/groovy/org/jetbrains/kotlin/NativeInteropPlugin.groovy

@@ -57,6 +57,10 @@ class NamedNativeInteropConfig implements Named {
     }
 
     void linkerOpts(String... values) {
+        this.linkerOpts(values.toList())
+    }
+
+    void linkerOpts(List<String> values) {
         linkerOpts.addAll(values)
     }