[VCRUNTIME] Add TLS callback support

sdk/lib/vcruntime/tlssup.c

@@ -0,0 +1,38 @@
+//
+// tlssup.c
+//
+//      Copyright (c) 2025 Timo Kreuzer
+//
+// TLS callback support
+//
+// SPDX-License-Identifier: MIT
+//
+
+#include <internal_shared.h>
+
+// Dummy TLS undex
+unsigned int _tls_index;
+
+// The TLS data
+_CRTALLOC(".tls") char *_tls_start = NULL;
+_CRTALLOC(".tls$ZZZ") char *_tls_end = NULL;
+
+// Describes the range of TLS callbacks.
+_CRTALLOC(".CRT$XLA") PIMAGE_TLS_CALLBACK __xl_a = 0;
+_CRTALLOC(".CRT$XLZ") PIMAGE_TLS_CALLBACK __xl_z = 0;
+
+//
+// The TLS directory.
+// The linker will point the executables TLS data directory entry to this.
+// Must be force-included with "#pragma comment(linker, "/INCLUDE:_tls_used")"
+// or by referencing it from another compilation unit.
+//
+const IMAGE_TLS_DIRECTORY _tls_used =
+{
+    (ULONG_PTR)&_tls_start,
+    (ULONG_PTR)&_tls_end,
+    (ULONG_PTR)&_tls_index,
+    (ULONG_PTR)(&__xl_a + 1),
+    (ULONG)0,
+    (ULONG)0
+};