allow installation of executables that are derived from the LLVM IR cmake rules

[compor]

allow installation of executables that are derived from the LLVM IR cmake rules

[compor]

this is better to be done on on a per target basis as needed by each target.
this is easy for top-level cmake targets created by the IR tools that are attached to existing targets.

for cases where the LLVM IR is required to be installed, an example is given in the cmake file CMakelists-loopcanon.txt used for exposition at commit a00d600