[Native][Tests] Make it possible to run LLVM Clang

Not all K/N targets have Clang in their toolchain. Thus,
we need to run the one from LLVM in our tests.

native/native.tests/tests/org/jetbrains/kotlin/konan/test/blackbox/AbstractNativeCExportTest.kt

@@ -22,6 +22,7 @@ import org.jetbrains.kotlin.konan.test.blackbox.support.runner.TestRunCheck
 import org.jetbrains.kotlin.konan.test.blackbox.support.runner.TestRunChecks
 import org.jetbrains.kotlin.konan.test.blackbox.support.settings.Timeouts
 import org.jetbrains.kotlin.konan.test.blackbox.support.settings.configurables
+import org.jetbrains.kotlin.konan.test.blackbox.support.util.ClangDistribution
 import org.jetbrains.kotlin.konan.test.blackbox.support.util.DEFAULT_MODULE_NAME
 import org.jetbrains.kotlin.konan.test.blackbox.support.util.compileWithClang
 import org.jetbrains.kotlin.konan.test.blackbox.support.util.getAbsoluteFile
@@ -68,6 +69,7 @@ abstract class AbstractNativeCExportTest(
         val includeDirectories = binaryLibrary.headerFile?.let { listOf(it.parentFile) } ?: emptyList()
         val libraryName = binaryLibrary.libraryFile.nameWithoutExtension.substringAfter("lib")
         compileWithClang(
+            clangDistribution = ClangDistribution.LlvmDistribution,
             sourceFiles = cSources,
             includeDirectories = includeDirectories,
             outputFile = executableFile,

native/native.tests/tests/org/jetbrains/kotlin/konan/test/blackbox/ObjCToKotlinSteppingInLLDBTest.kt

@@ -19,6 +19,7 @@ import org.jetbrains.kotlin.konan.test.blackbox.support.settings.LLDB
 import org.jetbrains.kotlin.konan.test.blackbox.support.settings.PipelineType
 import org.jetbrains.kotlin.konan.test.blackbox.support.settings.Timeouts
 import org.jetbrains.kotlin.konan.test.blackbox.support.settings.configurables
+import org.jetbrains.kotlin.konan.test.blackbox.support.util.ClangDistribution
 import org.jetbrains.kotlin.konan.test.blackbox.support.util.LLDBSessionSpec
 import org.jetbrains.kotlin.konan.test.blackbox.support.util.compileWithClang
 import org.junit.jupiter.api.Assumptions
@@ -224,6 +225,9 @@ class ObjCToKotlinSteppingInLLDBTest : AbstractNativeSimpleTest() {
         val executableFile = File(buildDir, clangExecutableName)
 
         compileWithClang(
+            // This code was initially written against clang from toolchain.
+            // Changing it to another one probably won't hurt, but it was not tested.
+            clangDistribution = ClangDistribution.Toolchain,
             sourceFiles = listOf(clangFile),
             outputFile = executableFile,
             frameworkDirectories = listOf(buildDir),

native/native.tests/tests/org/jetbrains/kotlin/konan/test/blackbox/support/util/Clang.kt

@@ -9,9 +9,27 @@ import org.jetbrains.kotlin.konan.test.blackbox.AbstractNativeSimpleTest
 import org.jetbrains.kotlin.konan.test.blackbox.support.settings.configurables
 import java.io.File
 
+/**
+ * Specifies which Clang should be used for compilation.
+ */
+internal enum class ClangDistribution {
+    /**
+     * Use Clang from target's toolchain.
+     * Note that not all targets do have a toolchain with Clang.
+     * For example, Apple targets do (from Xcode), and GCC-based Linux targets do not.
+     */
+    Toolchain,
+
+    /**
+     * Use Clang from Kotlin/Native LLVM distribution.
+     */
+    LlvmDistribution
+}
+
 // FIXME: absoluteTargetToolchain might not work correctly with KONAN_USE_INTERNAL_SERVER because
 // :kotlin-native:dependencies:update is not a dependency of :native:native.tests:test where this test runs
 internal fun AbstractNativeSimpleTest.compileWithClang(
+    clangDistribution: ClangDistribution = ClangDistribution.LlvmDistribution,
     sourceFiles: List<File>,
     outputFile: File,
     includeDirectories: List<File> = emptyList(),
@@ -20,8 +38,12 @@ internal fun AbstractNativeSimpleTest.compileWithClang(
     libraries: List<String> = emptyList(),
     additionalLinkerFlags: List<String> = emptyList(),
 ) {
+    val clang = when (clangDistribution) {
+        ClangDistribution.Toolchain -> "${testRunSettings.configurables.absoluteTargetToolchain}/bin/clang"
+        ClangDistribution.LlvmDistribution -> "${testRunSettings.configurables.absoluteLlvmHome}/bin/clang"
+    }
     val process = ProcessBuilder(
-        "${testRunSettings.configurables.absoluteTargetToolchain}/bin/clang",
+        clang,
         *sourceFiles.map { it.absolutePath }.toTypedArray(),
         *includeDirectories.flatMap { listOf("-I", it.absolutePath) }.toTypedArray(),
         "-isysroot", testRunSettings.configurables.absoluteTargetSysRoot,