Implement llvm and clang CLI helpers

HACKING.md

@@ -267,3 +267,22 @@ konanc main.kt -Xtemporary-files-dir=<PATH> -o <OUTPUT_NAME>
 ```shell script
 konanc main.kt -Xdisable-phases=BitcodeOptimization -Xoverride-clang-options=-c,-O2
 ```
+
+## Running Clang the same way Kotlin/Native compiler does
+
+Kotlin/Native compiler (including `cinterop` tool) has machinery that manages LLVM, Clang and native SDKs for supported targets
+and runs bundled Clang with proper arguments.
+To utilize this machinery, use `$dist/bin/run_konan clang $tool $target $arguments`, e.g.
+```
+$dist/bin/run_konan clang clang ios_arm64 1.c
+```
+will print and run the following command:
+```
+~/.konan/dependencies/clang-llvm-apple-8.0.0-darwin-macos/bin/clang \
+    -B/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin \
+    -fno-stack-protector -stdlib=libc++ -arch arm64 \
+    -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS13.5.sdk \
+    -miphoneos-version-min=9.0 1.c
+```
+
+The similar helper is available for LLVM tools, `$dist/bin/run_konan llvm $tool $arguments`.

utilities/cli-runner/src/main/kotlin/org/jetbrains/kotlin/cli/utilities/LlvmClang.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+package org.jetbrains.kotlin.cli.utilities
+
+import org.jetbrains.kotlin.konan.exec.Command
+import org.jetbrains.kotlin.konan.target.PlatformManager
+import org.jetbrains.kotlin.konan.util.KonanHomeProvider
+
+fun runLlvmTool(args: Array<String>) {
+    val toolName = args[0]
+    val toolArguments = args.drop(1)
+
+    val platform = platformManager().hostPlatform
+    val llvmHome = platform.configurables.absoluteLlvmHome
+
+    val toolPath = "$llvmHome/bin/$toolName"
+
+    runCommand(toolPath, *toolArguments.toTypedArray())
+}
+
+fun runLlvmClangToolWithTarget(args: Array<String>) {
+    val toolName = args[0]
+    val targetName = args[1]
+    val toolArguments = args.drop(2)
+
+    val platformManager = platformManager()
+    val platform = platformManager.platform(platformManager.targetByName(targetName))
+    val llvmHome = platform.configurables.absoluteLlvmHome
+
+    val toolPath = "$llvmHome/bin/$toolName"
+
+    runCommand(toolPath, *platform.clang.clangArgs, *toolArguments.toTypedArray())
+}
+
+private fun platformManager() = PlatformManager(KonanHomeProvider.determineKonanHome())
+
+private fun runCommand(vararg args: String) {
+    Command(*args)
+            .logWith { println(it()) }
+            .execute()
+}

utilities/cli-runner/src/main/kotlin/org/jetbrains/kotlin/cli/utilities/main.kt

@@ -29,6 +29,10 @@ private fun mainImpl(args: Array<String>, konancMain: (Array<String>) -> Unit) {
             defFileDependencies(utilityArgs)
         "generatePlatformLibraries" ->
             generatePlatformLibraries(utilityArgs)
+
+        "llvm" -> runLlvmTool(utilityArgs)
+        "clang" -> runLlvmClangToolWithTarget(utilityArgs)
+
         else ->
             error("Unexpected utility name")
     }