Four tailwindcss binaries downloaded (for all {linux,macos}-{arm64,x86} combinations)

[wikku]

#2765 was supposed to fix this with some trick.
If dune build is done in the tools/tailwindcss directory, only the correct build is downloaded.
But from the project root directory all four are downloaded.

Tested with dune 3.16 and 3.17.

$ dune bu --verbose
[...]
Actual targets:        
- alias @@default
Running[1]: (cd _build/default/tool/tailwind && /usr/bin/curl -sLO https://github.com/tailwindlabs/tailwindcss/releases/download/v3.3.6/tailwindcss-linux-arm64)
Running[2]: (cd _build/default/tool/tailwind && /usr/bin/curl -sLO https://github.com/tailwindlabs/tailwindcss/releases/download/v3.3.6/tailwindcss-linux-x64)
Running[3]: (cd _build/default/tool/tailwind && /usr/bin/curl -sLO https://github.com/tailwindlabs/tailwindcss/releases/download/v3.3.6/tailwindcss-macos-arm64)
Running[4]: (cd _build/default/tool/tailwind && /usr/bin/curl -sLO https://github.com/tailwindlabs/tailwindcss/releases/download/v3.3.6/tailwindcss-macos-x64)

[cuihtlauac]

Yes, you are right @wikku. PR #2765 did not do the job, I was mistaken.