[lldb] [cmake] Fix delayloading liblldb.dll in mingw builds (#162831)
ec28b95b7491bc2fbb6ec66cdbfd939e71255c42 made liblldb delayloaded, but
the supplied command line parameter is only valid for MSVC style builds.
For mingw builds using LLD, we can easily pass a similar option. For
mingw builds with ld.bfd, we can't quite as easily delayload it - for
these cases, just keep linking it like we usually do, and warn if the
user tried to set LLDB_PYTHON_DLL_RELATIVE_PATH in a build where it
won't have any effect.
Also change the setting for MSVC style builds, to use the simpler
`$<TARGET_FILE_NAME:liblldb>` instead of
`$<TARGET_FILE_BASE_NAME:liblldb>.dll`. The former pattern is what we
use for mingw targets, and it makes the code clearer to use that for
both, as that same expression should do the right thing for both.