fix: set sourcemap root to the workspace relative root_dir

[jbedard]

This makes the sourcemap sources and sourceRoot align with tsc (when invoked from ts_project EDIT: and not in a worker, and properly sandboxed, and probably other conditions for it to be the "normal" case). This is comparing a ts_project in silo, tsc vs swc

The sourcesContent is relative to the swc(root_dir), the sourceRoot is relative to the workspace root and includes the root_dir.

The map file sources is relative to the map, so when there is 1 .map per .js it is just the filename.
The sourceRoot is basically just a prefix and we just set it to what the user specifies (#177)

[thesayyn]

would be great to have a test where source_map_support is used.

[thesayyn]

LGTM

[realtimetodie]

I think this is a great solution and I added a small extra in #177. Let me know what you think.

[alexeagle]

Is this still draft, or is it ready to go?
Every time someone hits a TS worker bug I am dying to get rules_swc 1.0 out :)

[jbedard]

I put it into draft state because @thesayyn wasn't sure about the paths, see the ugly second commit which I'd like him to review.

Essentially we have to navigate from the .map file, out of the out_dir, and back to the original source (potentially in a root_dir). If the map was referencing the original .js files this would be essential, but the map files we're generating have the source embedded so technically it's isn't required for nice stack traces... I think? 😬

[thesayyn]

looks awesome

[alexeagle]

Looks like this broke Windows:

C:\tools\msys64\usr\bin\bash.exe -c external/aspect_rules_swc~override~swc~swc_win32-x64-msvc/swc-win32-x64-msvc.exe $@ < /dev/null  compile --source-maps false --source-file-name foo.ts --source-root  --config-file .swcrc --out-file bazel-out/x64_windows-fastbuild/bin/foo.js foo.ts
--
  | # Configuration: d00ace43f601efe48e0f1336609380be0dfba06ec5d3ce9d24364e336cd3c540
  | # Execution platform: @local_config_platform//:host
  | error: The argument '--source-root <SOURCE_ROOT>' requires a value but none was supplied

https://buildkite.com/bazel/bcr-presubmit/builds/1090#0186b799-ced5-4b38-8404-30c2129b62bb