[K/N] Separate ClangArgs for jni and native

Since LLVM for Windows is now native instead on MinGW, we have to
compile code in a different environment in case of JNI. This commits
just separates ClangArgs into two subclasses without actual behavior
changes.

kotlin-native/libclangext/build.gradle.kts

@@ -36,7 +36,7 @@ native {
     }
     suffixes {
         (".cpp" to ".$obj") {
-            tool(*platformManager.hostPlatform.clang.clangCXX("").toTypedArray())
+            tool(*platformManager.hostPlatform.clangForJni.clangCXX("").toTypedArray())
             flags(*cxxflags.toTypedArray(), "-c", "-o", ruleOut(), ruleInFirst())
         }
     }
@@ -47,7 +47,7 @@ native {
     }
     val objSet = sourceSets["main"]!!.transform(".cpp" to ".$obj")
     target(lib("clangext"), objSet) {
-        tool(*platformManager.hostPlatform.clang.llvmAr("").toTypedArray())
+        tool(*platformManager.hostPlatform.clangForJni.llvmAr("").toTypedArray())
         flags("-qv", ruleOut(), *ruleInAll())
     }
 }