This can matter on Windows:
- MSVC puts the binaries into subdirectories based on build type
(like "Debug" or "Release"), and then the test executables won't
find liblzma.dll because it's not in the working directory from
which the tests are run.
- With mingw-w64, liblzma.dll was in the working directory so the test
executables worked. However, the if the system happened to have
liblzma.dll in, for example, the Windows directory, then the DLL
search order might pick that instead.
Putting the shared library and test executables in the same directory
avoids these problems.
Reported-by: Frank <mail@franku.nl>
Fixes: https://github.com/tukaani-project/xz/pull/239