feat(linux): added fls() on Linux

components/linux/linux_include/strings.h

@@ -0,0 +1,23 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/*
+ * This is a helper include for fls(), which is present in the ESP-IDF toolchains and MacOS, but not on Linux.
+ */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int fls(unsigned int value);
+
+#ifdef __cplusplus
+}
+#endif
+
+#include_next <strings.h>