CI: remove Ubuntu 18 build and add macOS ARM build

Signed-off-by: Pavel Pisa <[email protected]>

Author: ppisa

.github/workflows/debug.yml

@@ -29,20 +29,19 @@ jobs:
             qt_version: "6.2.1"
           }
           - {
-            name: "Ubuntu 18 GCC",
-            os: ubuntu-18.04,
+            name: "macOS AMD64 Clang",
+            os: macos-13,
             build_type: "Debug",
-            cc: "gcc", cxx: "g++", build_system: "Unix Makefiles",
-            qt_version: "native",
-            qt_install_command: "sudo apt-get install qt5-default"
-              # Apt is significantly faster that aqt.
+            cc: "clang", cxx: "clang++", build_system: "Unix Makefiles",
+            qt_version: "5.15.2",
+            # Cached aqt is faster that brew.
           }
           - {
-            name: "macOS Latest Clang",
+            name: "macOS ARM Clang + Qt6",
             os: macos-latest,
             build_type: "Debug",
             cc: "clang", cxx: "clang++", build_system: "Unix Makefiles",
-            qt_version: "5.15.2",
+            qt_version: "6.6.3",
             # Cached aqt is faster that brew.
           }
           - {