Test build on macos-15

Author: m-kessler

.github/workflows/build.yml

@@ -10,7 +10,7 @@ jobs:
       matrix:
         include:
           - name: darwin64
-            image: macos-14
+            image: macos-15
             cmake-args: -G "Unix Makefiles" -D CMAKE_OSX_ARCHITECTURES=x86_64
     runs-on: ${{ matrix.image }}
     steps: