GHA/checksrc: use Linux for CI checks, merge job into misc checks

CI check used macOS before this patch, but with the help of Linuxbrew,
latest zizmor and shellcheck are also available on Linux.

Also:
- migrate CI checks to the misc check workflow, to make both shellcheck
  use the same, latest, shellcheck version, and to save the overhead of
  an extra workflow.

Closes #17911

.github/workflows/checksrc.yml

@@ -121,12 +121,27 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 5
     steps:
+      - name: 'install prereqs'
+        run: /home/linuxbrew/.linuxbrew/bin/brew install shellcheck zizmor
+
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
         with:
           persist-credentials: false
 
+      - name: 'zizmor GHA'
+        run: |
+          eval "$(/home/linuxbrew/.linuxbrew/bin/brew shellenv)"
+          zizmor --pedantic .github/workflows/*.yml
+
+      - name: 'shellcheck GHA'
+        run: |
+          eval "$(/home/linuxbrew/.linuxbrew/bin/brew shellenv)"
+          shellcheck --version
+          .github/scripts/shellcheck-ci.sh
+
       - name: 'shellcheck'
         run: |
+          eval "$(/home/linuxbrew/.linuxbrew/bin/brew shellenv)"
           shellcheck --version
           .github/scripts/shellcheck.sh
 
@@ -142,23 +157,3 @@ jobs:
           # shellcheck disable=SC2046
           grep -Ev '(\\bwill| url | dir )' .github/scripts/badwords.txt | \
           .github/scripts/badwords.pl $(git ls-files -- src lib include)
-
-  cicheck:
-    name: 'CI'
-    runs-on: macos-latest
-    timeout-minutes: 1
-    steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
-        with:
-          persist-credentials: false
-
-      - name: 'install prereqs'
-        run: brew install shellcheck zizmor
-
-      - name: 'zizmor GHA'
-        run: zizmor --pedantic .github/workflows/*.yml
-
-      - name: 'shellcheck GHA'
-        run: |
-          shellcheck --version
-          .github/scripts/shellcheck-ci.sh