llvm: Install scan-build and scan-view again

Also link them into the prefix so they can be used as normal programs.

> Currently these are not installed using make install, and are located in $(SRCDIR)/tools/clang/tools/scan-build and $(SRCDIR)/tools/clang/tools/scan-view respectively (where $(SRCDIR) is the root LLVM source directory). These locations are subject to change.

Bug: #25633
@adamv build with source problem?