* Source vendoring is passed as a standalone attribute to
`mkCargoDerivation`, meaning it does not automagically get spliced
with the correct local/cross system inputs (i.e. what would happen if
it was a `depsBuildBuild` entry)
* To fix this we need to make sure that `vendorCargoDeps` and all of its
transitive dependencies always use `runCommand` (and friends) from
their `pkgsBuildBuild` equivalent. This should always be safe to do
(even for cross-builds) since this amounts to building up a bunch of
sources which will be read by the build system
* Unfortunately I had to manually specify `pkgsBuildBuild.whatever` in
multiple places as I could not get things to work by messing with the
`callPackage` definition. Perhaps we should be using
`makeScopeWithSplicing'` instead of `makeScope` when constructing the
library, but I couldn't get it working (and I couldn't find any decent
docs on how to use it online) so this will make do for the time being.
* This should hopefully result in fewer surprises if someone is using a
really ancient toolchain for their code since we'll use whatever is in
nixpkgs to build craneUtils instead
Crates from git repos are vendored in a flattened directory where each crate shows up at the root of the vendor directory. Since the vendoring step effectively breaks workspace structures, any crates which use workspace inheritance (e.g. package.version.workspace = true will fail to resolve.
To work around this we inspect the crate's workspace manifest (if it exists) and attempt to manually merge the values while copying the contents to the vendor directory.
