set FGT linkage to PRIVATE

[hobu]

I'm doing some @conda-forge packaging of CPD for PDAL and I'm getting the following error

  The link interface of target "Cpd::Library-C++" contains:

    Fgt::Library-C++

  but the target was not found.  Possible reasons include:

    * There is a typo in the target name.
    * A find_package call is missing for an IMPORTED target.
    * An ALIAS target is missing.

Was there any specific reason the FGT linkage is PUBLIC instead of PRIVATE here? If it is PUBLIC for a reason, the Cpd-targets.cmake file is going to need to be updated to do a find_package(Fgt).

[gadomski]

If there was a reason, it is lost to the depths of time. Do you need a new release?

[hobu]

Do you need a new release?

I'm patching the recipes for now. Once I have them happy I'll ping you to bother with another release.