Temporarily break pure-rust-build for testing

This consists of several changes to verify that the
`pure-rust-build` CI job (still) works to verify that building
`max-pure` doesn't require tools it is not intended to require.

The main goal of this testing is to allow each step to be undone
after upgrading the Docker image to a newer version of Debian,
while verifying that doing so doesn't break or otherwise weaken
the test. See the individual commit messages below for details.

* Temporarily break `pure-rust-build` to verify that it can fail

This makes the `pure-rust-build` CI job attempt to install gitoxide
from `.` with implicit `max`, rather than explicit `max-pure`.

This job, introduced in ed4deac (GitoxideLabs#624), is intended to identify
unintended C toolchain dependencies. If, without the current
breakage, it is (still) capable of doing this, then as temporarily
modified here, it should fail. If it fails and the error messages
clearly relate to the absence of components necessary to build/use
C libraries, then it is probably (still) working.

Assuming it fails as expected, the Debian version can then be
increased, and then the changes here (and in any follow-up testing
adjustments) undone: if that fails, then succeeds, respectively,
then the job's functionality is most likely preserved across the
upgrade.

* Temporarily add `cmake` to `pure-rust-build` job

This needs to be undone, since `max-pure` definitely should not
require `cmake`. The reason for this temporary change is to figure
out how robust the test is: currently, it fails on `max` as it
should, but reports the absence of `cmake` as the reason. For the
test to be robust, its failure should be for a deeper reason, and
preferably even implicate the `minimal` Rust profile.

* Temporarily add `build-essential` to `pure-rust-build` job

This still installs `gcc` and `libc-dev` because `build-essential`
depends on them, but this als installs packages such as `g++` and
`make`, the absence of which seems to trigger failure before the
effects of installing the `minimal` toolchain do (if they do).

As in the previous change, this will of course need to be undone.

* Temporarily add `pkgconf` and `libssl-dev` to `pure-rust-build` job

This too must of course be undone. Like the last couple temporary
changes, this is to see if the significance of using the `minimal`
Rust toolchain can be identified.

Note: This causes the test to pass, even with the `minimal` Rust
toolchain. That's okay. These effects can be compared to those of
the reverse incremental changes to be made after increasing the
Debian image version.

.github/workflows/ci.yml

@@ -24,11 +24,11 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Prerequisites
-        run: apt-get update && apt-get install --no-install-recommends -y ca-certificates curl gcc libc-dev # gcc is required as OS abstraction
+        run: apt-get update && apt-get install --no-install-recommends -y ca-certificates curl build-essential pkgconf libssl-dev cmake # gcc is required as OS abstraction
       - name: install Rust via Rustup
         run: curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile minimal;
       - uses: Swatinem/rust-cache@v2
-      - run: /github/home/.cargo/bin/cargo install --debug --locked --no-default-features --features max-pure --path .
+      - run: /github/home/.cargo/bin/cargo install --debug --locked --path .
 
   test:
     runs-on: ubuntu-latest