[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/Interop/Indexer/build.gradle.kts

@@ -45,7 +45,7 @@ val libclang =
 
 val cflags = mutableListOf( "-I$llvmDir/include",
         "-I${project(":kotlin-native:libclangext").projectDir.absolutePath}/src/main/include",
-                            *platformManager.hostPlatform.clang.hostCompilerArgsForJni)
+                            *platformManager.hostPlatform.clangForJni.hostCompilerArgsForJni)
 
 val ldflags = mutableListOf("$llvmDir/$libclang", "-L${libclangextDir.absolutePath}", "-lclangext")
 
@@ -99,17 +99,15 @@ val lib = if (HostManager.hostIsMingw) "lib" else "a"
 
 native {
     val obj = if (HostManager.hostIsMingw) "obj" else "o"
-    val host = rootProject.project(":kotlin-native").extra["hostName"]
-    val hostLibffiDir = rootProject.project(":kotlin-native").extra["${host}LibffiDir"]
     val cxxflags = listOf("-std=c++11", *cflags.toTypedArray())
     suffixes {
         (".c" to ".$obj") {
-            tool(*platformManager.hostPlatform.clang.clangC("").toTypedArray())
+            tool(*platformManager.hostPlatform.clangForJni.clangC("").toTypedArray())
             flags(*cflags.toTypedArray(),
                   "-c", "-o", ruleOut(), ruleInFirst())
         }
         (".cpp" to ".$obj") {
-            tool(*platformManager.hostPlatform.clang.clangCXX("").toTypedArray())
+            tool(*platformManager.hostPlatform.clangForJni.clangCXX("").toTypedArray())
             flags(*cxxflags.toTypedArray(), "-c", "-o", ruleOut(), ruleInFirst())
         }
 
@@ -126,7 +124,7 @@ native {
                          sourceSets["main-cpp"]!!.transform(".cpp" to ".$obj"))
 
     target(solib("clangstubs"), *objSet) {
-        tool(*platformManager.hostPlatform.clang.clangCXX("").toTypedArray())
+        tool(*platformManager.hostPlatform.clangForJni.clangCXX("").toTypedArray())
         flags(
             "-shared",
             "-o", ruleOut(), *ruleInAll(),