[windows] add PDB files to install target

[charles-zablit]

This is part of swiftlang/swift#88869.

[stmontgomery]

I can understand why we would want symbol files for the testing library itself, i.e. the Testing module, since that's linked in to test processes that Swift users may need to debug through. But I'm unclear why we need to include one for the macro plugin (TestingMacros) since it's used at build time and user code isn't loaded into that process. Can you elaborate there?

[grynspan]

@compnerd Please advise!

[charles-zablit]

I can understand why we would want symbol files for the testing library itself, i.e. the Testing module, since that's linked in to test processes that Swift users may need to debug through. But I'm unclear why we need to include one for the macro plugin (TestingMacros) since it's used at build time and user code isn't loaded into that process. Can you elaborate there?

I'm not familiar with this part of the toolchain. The overall goal of the debug symbol server is to provide debug symbols for users of the toolchain as well as maintainers. We will also provide debug symbols for lldb and swiftc for instance.