CI: speed up gcc and clang-format Ubuntu runs

This is an attempt to speed up the gcc and clang-format CI jobs on the
Ubuntu runner, which spends between 2 and 3 minutes on apt-get update and
apt-get install.

Without apt-get update, the installation of the dependencies (ccache, z3,
clang-format) now takes 20 seconds.

Author: kroening

.github/workflows/pull-request-checks.yaml

@@ -19,10 +19,17 @@ jobs:
           # user input
           DEBIAN_FRONTEND: noninteractive
         run: |
-          sudo apt-get update
-          sudo apt-get install --no-install-recommends -yq gcc gdb g++ jq flex bison libxml2-utils ccache cmake z3
+          sudo apt-get remove --purge man-db
+          packages_to_install="ccache z3"
+          if ! sudo apt-get install --no-install-recommends -yq $packages_to_install ; then
+            # retry after updating package indices
+            sudo apt-get update
+            sudo apt-get install --no-install-recommends -yq $packages_to_install
+          fi
       - name: Confirm z3 solver is available and log the version installed
         run: z3 --version
+      - name: Log the version of gcc
+        run: gcc --version
       - name: Prepare ccache
         uses: actions/cache@v4
         with:
@@ -77,8 +84,13 @@ jobs:
           # user input
           DEBIAN_FRONTEND: noninteractive
         run: |
-          sudo apt-get update
-          sudo apt-get install --no-install-recommends -yq clang-19 clang++-19 gdb jq flex bison libxml2-utils cpanminus ccache z3
+          sudo apt-get remove --purge man-db
+          packages_to_install="clang-19 clang++-19 gdb jq flex bison libxml2-utils cpanminus ccache z3"
+          if ! sudo apt-get install --no-install-recommends -yq $packages_to_install ; then
+            # retry after updating package indices
+            sudo apt-get update
+            sudo apt-get install --no-install-recommends -yq $packages_to_install
+          fi
           cpanm Thread::Pool::Simple
       - name: Confirm z3 solver is available and log the version installed
         run: z3 --version

.github/workflows/syntax-checks.yaml

@@ -18,8 +18,13 @@ jobs:
           # user input
           DEBIAN_FRONTEND: noninteractive
         run: |
-          sudo apt-get update
-          sudo apt-get install --no-install-recommends -yq clang-format-15
+          sudo apt-get remove --purge man-db
+          packages_to_install="clang-format-15"
+          if ! sudo apt-get install --no-install-recommends -yq $packages_to_install ; then
+            # retry after updating package indices
+            sudo apt-get update
+            sudo apt-get install --no-install-recommends -yq $packages_to_install
+          fi
       - name: Check updated lines of code match clang-format-15 style
         env:
           BASE_BRANCH: ${{ github.base_ref }}