refactor(linux): Unified libbsd handling

* Users can now use libbsd string.h and sys/cdefs.h functionality
  (e.g., strlcpy, containerof) on Linux by just including
  string.h or sys/cdefs.h. In other words, the includes are the same
  on the Linux target as well as on chips targets (ESP32, etc.).
* libbsd linking is done by the linux component (belongs to common
  components) now instead of handling it separately in each component

components/linux/CMakeLists.txt

@@ -14,3 +14,12 @@ endif()
 idf_component_register(INCLUDE_DIRS ${includes}
                        REQUIRED_IDF_TARGETS linux
                        SRCS ${srcs})
+
+if(${IDF_TARGET} STREQUAL "linux")
+    find_library(LIB_BSD bsd)
+    if(LIB_BSD)
+        target_link_libraries(${COMPONENT_LIB} PRIVATE ${LIB_BSD})
+    elseif(NOT CMAKE_HOST_SYSTEM_NAME STREQUAL "Darwin")
+        message(WARNING "Missing LIBBSD library. Install libbsd-dev package and/or check linker directories.")
+    endif()
+endif()

components/linux/include/esp_linux_helper.h

@@ -1,10 +1,16 @@
 /*
- * SPDX-FileCopyrightText: 2022-2023 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2024 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 #pragma once
 
+/*
+ * NOTE: This file is deprecated and will be removed in the future.
+ *       Use include sys/cdefs.h instead, it will also include
+ *       the corresponding libbsd header. TODO: IDF-9391
+ */
+
 #ifdef __cplusplus
 extern "C" {
 #endif

components/linux/linux_include/string.h

@@ -0,0 +1,15 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/*
+ * This header file also includes the additional libbsd string.h with functions such as strlcpy(),
+ * which are present in the ESP-IDF toolchain and on MacOS, but not on Linux.
+ */
+
+#pragma once
+
+#include <bsd/string.h>
+#include_next <string.h>

components/linux/linux_include/sys/cdefs.h

@@ -0,0 +1,22 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/*
+ * This header file adds the libbsd defines of header cdefs.h.
+ * It also defines __uintptr_t which is still used by older libbsd versions (< 0.11.3)
+ * but not (or not guaranteed to be) defined on Linux.
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+// We need a define. We can't typedef here since, depending on the include order,
+// uintptr_t may not be defined yet.
+#define __uintptr_t uintptr_t
+
+#include_next <sys/cdefs.h>
+#include <bsd/sys/cdefs.h>