[CMake] User-overriding IMPORTED targets (overlaying libraries, ...)

[Stephen Kelly]

Ivan Shapovalov wrote:

> Of course, I can always edit the FooConfig.cmake file manually, but I'd
> better avoid patching anything (installing new files or running any
> cmake commands is OK).
> 
> Is there any nice way to solve this?

After 

 find_package(Foo CONFIG)

do

 set_property(TARGET Foo::Foo PROPERTY LOCATION "foo_overlay.so")

Apply whatever platform-specific conditions, suffix and prefix are 
appropriate.

Thanks,

Steve.