cargo_bootstrap fails when rules_rust is pulled in via git_override

It builds the cargo-bazel binary, but then fails to find it somehow:

```
Compiling cargo-bazel v0.16.0 (/home/chipc/.cache/bazel/_bazel_chipc/fb1197929d86973fc3e8ae030fa837b7/external/rules_rust+/crate_universe)
Finished `release` profile [optimized] target(s) in 5.56s
INFO: Repository rules_rust++cu_nr+cargo_bazel_bootstrap instantiated at:
: in
Repository rule cargo_bootstrap_repository defined at:
/home/chipc/.cache/bazel/_bazel_chipc/fb1197929d86973fc3e8ae030fa837b7/external/rules_rust+/cargo/private/cargo_bootstrap.bzl:240:45: in
ERROR: /home/chipc/.cache/bazel/_bazel_chipc/fb1197929d86973fc3e8ae030fa837b7/external/rules_rust+/cargo/private/cargo_bootstrap.bzl:111:13: An error occurred during the fetch of repository 'rules_rust++cu_nr+cargo_bazel_bootstrap':
Traceback (most recent call last):
File "/home/chipc/.cache/bazel/_bazel_chipc/fb1197929d86973fc3e8ae030fa837b7/external/rules_rust+/cargo/private/cargo_bootstrap.bzl", line 220, column 35, in _cargo_bootstrap_repository_impl
built_binary = cargo_bootstrap(
File "/home/chipc/.cache/bazel/_bazel_chipc/fb1197929d86973fc3e8ae030fa837b7/external/rules_rust+/cargo/private/cargo_bootstrap.bzl", line 111, column 13, in cargo_bootstrap
fail("Failed to produce binary at {}".format(binary_path))
Error in fail: Failed to produce binary at release/cargo-bazel
ERROR: no such package '@@rules_rust++cu_nr+cargo_bazel_bootstrap//': Failed to produce binary at release/cargo-bazel
ERROR: /home/chipc/workspaces/kopernikus/svi-depot/ext/rust/BUILD:3:14: //ext/rust:crates_vendor depends on @@rules_rust++cu_nr+cargo_bazel_bootstrap//:binary in repository @@rules_rust++cu_nr+cargo_bazel_bootstrap which failed to fetch. no such package '@@rules_rust++cu_nr+cargo_bazel_bootstrap//': Failed to produce binary at release/cargo-bazel
WARNING: errors encountered while analyzing target '//ext/rust:crates_vendor', it will not be built.
Analysis failed
INFO: Analyzed target //ext/rust:crates_vendor (97 packages loaded, 2467 targets configured).
INFO: Found 0 targets...
ERROR: command succeeded, but there were loading phase errors
INFO: Elapsed time: 8.220s, Critical Path: 0.00s
INFO: 1 process: 1 internal.
ERROR: Build did NOT complete successfully
ERROR: Build failed. Not running target
```