Native: remove support for pre-Xcode 12 libclang_rt

Kotlin/Native doesn't support Xcode versions older than 12.5 anymore,
so just remove the obsolete code.

kotlin-native/shared/src/main/kotlin/org/jetbrains/kotlin/konan/target/Linker.kt

@@ -187,10 +187,9 @@ class MacOSBasedLinker(targetProperties: AppleConfigurables)
             Family.OSX -> "osx"
             else -> error("Target $target is unsupported")
         }
-        // TODO: remove after `minimalXcodeVersion` will be 12.
         // Separate libclang_rt version for simulator appeared in Xcode 12.
-        val compilerRtForSimulatorExists = Xcode.current.version.substringBefore('.').toInt() >= 12
-        val suffix = if ((libraryName.isNotEmpty() || compilerRtForSimulatorExists) && targetTriple.isSimulator) {
+        // We don't support Xcode versions older than 12.5 anymore, so no need to check Xcode version.
+        val suffix = if (targetTriple.isSimulator) {
             "sim"
         } else {
             ""