Instead of execClang we now have execKonanClang which properly invokes

the distribution clang able to utilize distributed sysroots etc.
And execBareClang which just invokes the distribution clang with system sysroot.

backend.native/tests/build.gradle

@@ -2286,7 +2286,7 @@ if (isMac()) {
         interop = 'objcSmoke'
 
         doFirst {
-            execClang {
+            execKonanClang(project.testTarget) {
                 args "$projectDir/interop/objc/smoke.m"
                 args "-lobjc", '-fobjc-arc'
                 args '-fPIC', '-shared', '-o', "$buildDir/libobjcsmoke.dylib"