misc: add lineSeparator to Filesystem (#1267)

Author: lauzadis

runtime/runtime-core/api/runtime-core.api

@@ -2392,6 +2392,10 @@ public final class aws/smithy/kotlin/runtime/util/OsFamily : java/lang/Enum {
 public abstract interface class aws/smithy/kotlin/runtime/util/PlatformEnvironProvider : aws/smithy/kotlin/runtime/util/EnvironmentProvider, aws/smithy/kotlin/runtime/util/PropertyProvider {
 }
 
+public final class aws/smithy/kotlin/runtime/util/PlatformKt {
+	public static final fun getLineSeparator (Laws/smithy/kotlin/runtime/util/OperatingSystem;)Ljava/lang/String;
+}
+
 public abstract interface class aws/smithy/kotlin/runtime/util/PlatformProvider : aws/smithy/kotlin/runtime/util/Filesystem, aws/smithy/kotlin/runtime/util/PlatformEnvironProvider {
 	public static final field Companion Laws/smithy/kotlin/runtime/util/PlatformProvider$Companion;
 	public abstract fun isAndroid ()Z

runtime/runtime-core/common/src/aws/smithy/kotlin/runtime/util/Platform.kt

@@ -52,6 +52,15 @@ internal expect object SystemDefaultProvider : PlatformProvider {
 
 public data class OperatingSystem(val family: OsFamily, val version: String?)
 
+/**
+ * The string which represents a line separator on this file system. For example, on Windows, this is CRLF.
+ */
+public val OperatingSystem.lineSeparator: String
+    get() = when {
+        family == OsFamily.Windows -> "\r\n"
+        else -> "\n"
+    }
+
 public enum class OsFamily {
     Linux,
     MacOs,