[mono] Implement Environment.GetFolderPath on iOS (#34022)

* Implement Environment.GetFolderPath on iOS

* Address feedback

* Move GetFolderPathCore to Environment.Unix.GetFolderPathCore.cs

* Fix build issue

* Address feedback

* cache all special directories

* Fix build issue

* remove a whitespace

* Fix UserProfile issue

* undo changes in GetEnvironmentVariableCore

* Update Environment.Unix.Mono.cs

* Extract to InternalGetEnvironmentVariable

* Fix build issue

* Return emtpy string if underlying native function returns null

* Add nullability

1 files changed, 14 insertions, 0 deletions

diff --git a/src/libraries/Native/Unix/System.Native/pal_searchpath.m b/src/libraries/Native/Unix/System.Native/pal_searchpath.m
new file mode 100644
index 00000000000..a4f150da764
--- /dev/null
+++ b/src/libraries/Native/Unix/System.Native/pal_searchpath.m
@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include "pal_searchpath.h"
+#import <Foundation/Foundation.h>
+
+const char* SystemNative_SearchPath(int32_t folderId)
+{
+    NSSearchPathDirectory spd = (NSSearchPathDirectory) folderId;
+    NSURL* url = [[[NSFileManager defaultManager] URLsForDirectory:spd inDomains:NSUserDomainMask] lastObject];
+    const char* path = [[url path] UTF8String];
+    return path == NULL ? NULL : strdup (path);
+}