CI: a writable CARGO_HOME, so the portal git dependency can be fetched

The shared /var/local/cargo is read-only for the runner; 0.1.1 built
only because this machine had already cloned the same portal tag into
it.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01L4jrCgLiKKHAEFuZUJjckH

.gitea/workflows/publish.yml

@@ -12,7 +12,9 @@ jobs:
   publish:
     runs-on: bare
     env:
-      CARGO_HOME: /var/local/cargo
+      # Writable, unlike the shared /var/local/cargo - see test.yml.
+      CARGO_HOME: /var/local/cargo-target/iris-cargo-home
+      RUSTC_WRAPPER: /usr/bin/sccache
       RUSTUP_HOME: /var/local/rustup
       PATH: /var/local/cargo/bin:/usr/local/sbin:/usr/local/bin:/usr/bin
       SCCACHE_DIR: /var/local/sccache

.gitea/workflows/test.yml

@@ -10,7 +10,12 @@ jobs:
     runs-on: bare
     env:
       # Same shared toolchain and cache as uhhm/portal's workflows.
-      CARGO_HOME: /var/local/cargo
+      # Not the shared /var/local/cargo: the runner may only read it, and
+      # the portal git dependency has to be cloned into CARGO_HOME. This
+      # one lives under the writable target dir; the rustc wrapper the
+      # shared config would have set is given here instead.
+      CARGO_HOME: /var/local/cargo-target/iris-cargo-home
+      RUSTC_WRAPPER: /usr/bin/sccache
       RUSTUP_HOME: /var/local/rustup
       PATH: /var/local/cargo/bin:/usr/local/sbin:/usr/local/bin:/usr/bin
       SCCACHE_DIR: /var/local/sccache