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.

Author: EliahKagan

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Prerequisites
-        run: apt-get update && apt-get install --no-install-recommends -y ca-certificates curl build-essential cmake # 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