[windows] Building the toolchain with `-DebugInfo` takes up to 64GB of RAM

[charles-zablit]

When building the toolchain with -DebugInfo, during the compiler build phase, linking takes up to 64GB of RAM.

This can be mitigated by lowering LLVM_PARALLEL_LINK_JOBS and SWIFT_PARALLEL_LINK_JOBS (see #86959).

The memory pressure is not this high on other platforms.