lib: introduce io library

The `io` library wraps UNIX file descriptors and provides access to
non-stdio descriptor operations such as `read(2)`, `write(2)`,
`fcntl(2)` etc.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

Author: jow-

CMakeLists.txt

@@ -71,6 +71,7 @@ endif()
 
 option(DEBUG_SUPPORT "Debug plugin support" ON)
 option(FS_SUPPORT "Filesystem plugin support" ON)
+option(IO_SUPPORT "IO plugin support" ON)
 option(MATH_SUPPORT "Math plugin support" ON)
 option(UBUS_SUPPORT "Ubus plugin support" ${DEFAULT_UBUS_SUPPORT})
 option(UCI_SUPPORT "UCI plugin support" ${DEFAULT_UCI_SUPPORT})
@@ -163,6 +164,13 @@ if(FS_SUPPORT)
   target_link_options(fs_lib PRIVATE ${UCODE_MODULE_LINK_OPTIONS})
 endif()
 
+if(IO_SUPPORT)
+  set(LIBRARIES ${LIBRARIES} io_lib)
+  add_library(io_lib MODULE lib/io.c)
+  set_target_properties(io_lib PROPERTIES OUTPUT_NAME io PREFIX "")
+  target_link_options(io_lib PRIVATE ${UCODE_MODULE_LINK_OPTIONS})
+endif()
+
 if(MATH_SUPPORT)
   set(LIBRARIES ${LIBRARIES} math_lib)
   add_library(math_lib MODULE lib/math.c)