lib posix: Allow building the POSIX_API library without the host libC

In theory one may want to build the POSIX compability shim
with a different C library than one provided with Zephyr,
so let's not prevent it.

Signed-off-by: Alberto Escolar Piedras <[email protected]>

Author: aescolar

lib/CMakeLists.txt

@@ -6,6 +6,8 @@ add_compile_options($<TARGET_PROPERTY:compiler,warning_shadow_variables>)
 add_subdirectory(crc)
 if(NOT CONFIG_EXTERNAL_LIBC)
 add_subdirectory(libc)
+endif()
+if(NOT CONFIG_NATIVE_LIBC)
 add_subdirectory(posix)
 endif()
 add_subdirectory_ifdef(CONFIG_CPP                  cpp)