Fix audio support for squeak3
Sound support comes to do squeak3(squeak-3.5) porting, but
does not become effective because, actually, it cannot
detect the library which I am going to utilize with stage
of configure.
PR: ports/46180,ports/53474
Submitted by: NINOMIYA Hideyuki <nin@Jp.FreeBSD.org>,parv <parv_fm@emailgroups.net>