Find the home directory instead of hard-coding it

This should make the `setup-trunk` workflow more container-independent.

.forgejo/setup-trunk/action.yaml

@@ -10,5 +10,13 @@ runs:
   using: "composite"
   steps:
     - run: rustup target add wasm32-unknown-unknown
+    # Forgejo Runner seems to modify the HOME variable when it's running a job
+    # in a Docker container, so we have to find the home directory another way,
+    # inspired by this StackOverflow answer:
+    #
+    #   https://unix.stackexchange.com/a/247582
+    #
+    - id: find-home
+      run: eval echo "home=~$(whoami)" >> $GITHUB_OUTPUT
     - run: curl --output - --proto '=https' --tlsv1.2 --retry 10 --retry-connrefused --location --silent --show-error --fail 'https://github.com/trunk-rs/trunk/releases/download/v0.21.12/trunk-x86_64-unknown-linux-gnu.tar.gz' | tar --gunzip --extract --file -
-      working-directory: /home/circleci/.cargo/bin
+      working-directory: ${{ steps.find-home.outputs.home }}/.cargo/bin