Static libraries don't have PDB files. A PDB that would previously end
up installed alongside a static library belonged in fact to the dynamic
version of the same library built at the same time.
This was because the former minstall.Installer implementation, when
installing a file target, also blindly copied any *.pdb file it found
whose filename was matching the target. So, for example installing
foo.dll and foo.a would also install two copies of foo.pdb into both
bin/ and lib/, which doesn't seem like the right thing to do - foo.pdb
should only get installed with foo.dll.
On Windows, if we are going to link with a shared module, we need the
implib.
Use case: The Xorg server builds some X protocol extensions as modules. The
implibs for these modules need to be shipped as part of the SDK, to enable
building of 3rd party extensions which reference symbols in (and hence on
Windows, need to be linked with) these modules.