Missing package_type assignment in example documentation of "Package prebuilt binaries"

[luizfeldmann]

The example of Package prebuilt binaries does not mention the need to set an appropriate package_type.

In case the package_type remains undefined, consumers using CMakeDeps generator will not have the a _BIN_DIRS variable defined in the generated finders, due to the explicit exclusion of such variable in target_data.py:346.

As a result, users trying to use the example documentation to package a pre-existing shared library will most likely fail to run the test_package due to a missing DLL.

[memsharded]

Thanks @luizfeldmann for pointing out this issue. This needs to be fixed first in the examples2 repo, then in the docs. It needs to be package_type = "static-library" in the examples, and then briefly explained in the docs, linking to the package_type docs.