zlib.dll szip.dll hdf5.dll and hdf5_hl.dll are being used by another process

When the unit test of my own method using HDF.PInvoke is executed, cleaning the solution will raise the error "Unable to delete file "\Hdf5.Tests\bin\Debug\bin64\zlib.dll". Access to the path '\Hdf5.Tests\bin\Debug\bin64\zlib.dll' is denied. "

Checking out the source code of HDF.PInvoke, running the unit tests and cleaning solution, will give the same error.

Reproduce the issue by checking out HDF.PInvoke, running its unit tests, and cleaning the solution. Start with the files or test setup that place zlib.dll, szip.dll, hdf5.dll, and hdf5_hl.dll under Hdf5.Tests/bin/Debug/bin64; done means cleaning can delete those files without an access-denied error.

Written by the indexing model from the issue text.