Ignore non-code paths in QEMU test CI action (theseus-os#1063)

* The QEMU test workflow won't run if the changes only include:
- 'book/**'
- 'c_test/**'
- 'docker/**'
- 'github_pages/**'
- 'old_crates/**'
- 'scripts/**'
- '.gitignore'
- 'LICENSE-MIT'
- 'README.md'
- 'bochsrc.txt'
- 'rustfmt.toml'
- 'slirp.conf'

We specify ignore paths conservatively in order to avoid other paths
inadvertently affecting the CI action, which could lead to issues.

Signed-off-by: Klimenty Tsoutsman <[email protected]>

.github/workflows/test.yaml

@@ -2,6 +2,19 @@ name: QEMU Test
 on:
   pull_request:
     types: [synchronize, opened, reopened]
+    paths-ignore:
+      - 'book/**'
+      - 'c_test/**'
+      - 'docker/**'
+      - 'github_pages/**'
+      - 'old_crates/**'
+      - 'scripts/**'
+      - '.gitignore'
+      - 'LICENSE-MIT'
+      - 'README.md'
+      - 'bochsrc.txt'
+      - 'rustfmt.toml'
+      - 'slirp.conf'
 jobs:
   run-tests:
     runs-on: ubuntu-latest