Update lib.rs
Update lib.rs

Change error message after readme changes in bc6a3a5a5455a2db423b713911821215a1b48fca so pointing to new section
alexcrichton/gcc-rs,kosta/gcc-rs,alexcrichton/gcc-rs,gabrielesvelto/gcc-rs,kosta/gcc-rs,kosta/gcc-rs,gabrielesvelto/gcc-rs,alexcrichton/gcc-rs,gabrielesvelto/gcc-rs