Procedural macros are rebuilding all dependencies

[shepmaster]

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[shepmaster]

@dtolnay identified the problem (lightly edited by me):

From the changelog

Debuginfo for build dependencies is now off if not explicitly set. This is expected to improve the overall build time. #11252

That Cargo change means that when the playground image is built with its hundreds of dependencies, the subset of them which were not build dependencies are built with debug = true. However when a user later runs a build in the playground containing a proc macro, those same hundreds of dependencies would now be treated by Cargo as build dependencies, because they are dependencies of a proc macro now, resulting in a different setting for debuginfo and unable to reuse the precompiled copies.

To reuse the same prebuilt crates as both ordinary dependencies and dependencies of a macro, both would need to be set to build with the same setting for debuginfo

Try this to get the same behavior as before:

[profile.dev.build-override]
debug = true