dns/dsc: Fix DEPENDS order

[leres]

Summary

Proposed commit message:

Put LIB_DEPENDS after BUILD_DEPENDS as per mat@ (and the Porter's
Handbook).

PR:		
Submitted by:	
Reported by:	mat
Reviewed by:	? (mentor)
Approved by:	? (mentor)
Obtained from:	
MFC after:	
MFH:		
Relnotes:	
Security:	
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Differential Revision:	?

[matthew]

You've got implicit mentor approval for commiting this sort of simple update -- no need to put it to a review.