Skip LLVM test if required modules aren't found
Skip LLVM test if required modules aren't found

If the required LLVM modules can't be found, skip the LLVM framework
test, rather than succesfully doing nothing.

(This optionality is a leftover from before #7379)

(At the moment, OpenSuse provides dynamic-only LLVM.  The cmake method
still finds LLVM, when a static LLVM is requested, but fails to find any
modules.  This might be a bug in the cmake method of the LLVM
dependency.)

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