Add compat bits for libtls on Windows

tls/compat/getuid.c

@@ -0,0 +1,14 @@
+/*
+ * Public domain
+ *
+ * Kinichiro Inoguchi <inoguchi@openbsd.org>
+ */
+
+#include <unistd.h>
+
+uid_t
+getuid(void)
+{
+	/* Windows fstat sets 0 as st_uid */
+	return 0;
+}