chore: some more kotlin native extension utils

Author: sureshg

backend/native/src/linuxMain/kotlin/Env.kt

@@ -1,4 +1,16 @@
-import kotlinx.cinterop.toKString
-import platform.posix.getpass
+import kotlin.time.Instant
+import kotlinx.cinterop.*
+import kotlinx.io.files.Path
+import platform.posix.*
 
 actual fun readPassword(prompt: String) = getpass(prompt)?.toKString()
+
+fun getMTime(path: Path): Instant {
+  memScoped {
+    val stat = alloc<stat>()
+    if (lstat(path.toString(), stat.ptr) != 0) {
+      throw IllegalStateException("Failed to get mtime for $path")
+    }
+    return Instant.fromEpochSeconds(stat.st_mtim.tv_sec, stat.st_mtim.tv_nsec)
+  }
+}

backend/native/src/nativeMain/kotlin/io/IO.kt

@@ -1,7 +1,6 @@
-import kotlin.test.assertEquals
-import kotlinx.io.Buffer
+import kotlin.test.*
+import kotlinx.io.*
 import kotlinx.io.files.*
-import kotlinx.io.readFloat
 
 fun buffer() {
   val buffer = Buffer()
@@ -14,3 +13,7 @@ fun dir() {
   println("SystemTemporaryDirectory: $SystemTemporaryDirectory")
   SystemFileSystem.list(Path(".")).forEach { println(it) }
 }
+
+fun Path.append(data: String) {
+  SystemFileSystem.sink(this, append = true).buffered().use { f -> f.writeString(data) }
+}