llvm12: adjust cmake library paths
llvm12: adjust cmake library paths

This is related to issue #3749. The fixed packages were tested on x86_64 by
building a couple of language servers(ccls and irony-server) which use these
library paths.

haikuports/haikuports,haikuports/haikuports,haikuports/haikuports,haikuports/haikuports,Begasus/haikuports,Begasus/haikuports,Begasus/haikuports,Begasus/haikuports,Begasus/haikuports,haikuports/haikuports