install,export: Maybe transform OBJECT libraries to INTERFACE libraries
Teach the install
and export
commands to support installing and
exporting OBJECT
libraries without their object files. Transform
them to INTERFACE
libraries in such cases.
For install(TARGETS)
, activate this when no destination for the object
files is specified. For export
, activate this only under Xcode with
multiple architectures when we have no well-defined object file
locations to give to clients.