Use macOS 15 on all macOS jobs

Author: FelixHerrmann

.github/workflows/release-build.yml

@@ -7,7 +7,7 @@ on:
 jobs:
   release-build:
     name: Release Build
-    runs-on: macos-15
+    runs-on: macos-26
     outputs:
       sha: ${{ steps.sha256.outputs.sha256 }}
     env:

.github/workflows/xcodebuild.yml

@@ -32,7 +32,7 @@ jobs:
           - generic/platform=tvOS
           - generic/platform=watchOS
           - generic/platform=visionOS
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
       - uses: maxim-lobanov/setup-xcode@v1
         with:
@@ -47,7 +47,7 @@ jobs:
   test:
     name: Test
     needs: build-libraries
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
       - uses: maxim-lobanov/setup-xcode@v1
         with: