Add missing autogen call to MacOS action

Author: PhilipHazel

.github/workflows/build.yml

@@ -69,6 +69,9 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v3
+        
+      - name: Prepare
+        run: ./autogen.sh
 
       - name: Configure
         run: cmake -DPCRE2_SUPPORT_JIT=ON -DPCRE2_BUILD_PCRE2_16=ON -DPCRE2_BUILD_PCRE2_32=ON -DCMAKE_OSX_ARCHITECTURES='arm64;x86_64' -DCMAKE_C_FLAGS='-Wall -Wextra' -B build