ts_library source mapped files are now read only instead of symlinks to the source file

[Toxicable]

When debugging a nodejs application via the VS Code debugger, when you hit a breakpoint, the debugger will take you to a readonly source mapped file.
This is terribly un ergonomic since you must then manually navigate to the source file before you can make any changes.

I believe this now superseeds bazelbuild/rules_typescript#254

This only started happening from the upgrade of rules_typescript=0.10.1 to current.
While the old issue of having source maps point to a symlinked file was also a unergonomic way to handle it, this is even worse and a blocker for us upgrading.
The ideal situation would be for source maps to point back to the source file

[Toxicable]

The cause of this issue is actaully when preserve_symlinks=False is set in node_repositories.

[Toxicable]

The latest update in rules_typescript from 0.21.0 -> 0.22.0 have broken the above work around.
This commit here: bazelbuild/rules_typescript@676567c
I have a repo of it broken here: https://github.com/Toxicable/bug-bazel_source_maps

cc @vikerman

[Toxicable]

superseeded by #823