Split clang-tidy workflow into two parts

The full clang-tidy run takes too long, so split it into one part for
src and one for everything else.

.github/workflows/clang-tidy.yml

@@ -39,12 +39,20 @@ jobs:
     needs: skip-duplicates
     if: ${{ needs.skip-duplicates.outputs.should_skip != 'true' }}
 
+    strategy:
+      fail-fast: true
+      matrix:
+        # To make the run finish in the run time limit, we split it up into two
+        # parts: the src directory and everything else
+        subset: [ 'src', 'other' ]
+
     runs-on: ubuntu-20.04
     env:
         CMAKE: 1
         CLANG: clang++-12
         COMPILER: clang++-12
         CATA_CLANG_TIDY: plugin
+        CATA_CLANG_TIDY_SUBSET: ${{ matrix.subset }}
         TILES: 1
         SOUND: 1
         RELEASE: 1

build-scripts/clang-tidy.sh

@@ -121,6 +121,19 @@ else
     fi
 fi
 
+printf "Subset to analyze: '%s'\n" "$CATA_CLANG_TIDY_SUBSET"
+
+# We might need to analyze only a subset of the files if they have been split
+# into multiple jobs for efficiency
+case "$CATA_CLANG_TIDY_SUBSET" in
+    ( src )
+        tidyable_cpp_files=$(printf '%s\n' "$tidyable_cpp_files" | grep '/src/')
+        ;;
+    ( other )
+        tidyable_cpp_files=$(printf '%s\n' "$tidyable_cpp_files" | grep -v '/src/')
+        ;;
+esac
+
 function analyze_files_in_random_order
 {
     if [ -n "$1" ]