extmod/vfs_posix: Include errno.h and unistd.h headers.

errno.h is needed for the errno variable, and unistd.h is needed for chdir.

Signed-off-by: Damien George <damien@micropython.org>

extmod/vfs_posix.c

@@ -37,9 +37,11 @@
 #error "MICROPY_VFS_POSIX requires MICROPY_ENABLE_FINALISER"
 #endif
 
+#include <errno.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/stat.h>
+#include <unistd.h>
 #include <dirent.h>
 #ifdef _MSC_VER
 #include <direct.h> // For mkdir etc.