Exclude Qt versions not supported by Qt's online installer

Thus, not supported by aqtinstall, and thus not supported by
install-qt-action.

.github/workflows/build.yaml

@@ -41,6 +41,21 @@ jobs:
         cc:
           - clang
           - gcc
+        exclude:
+          # Qt's online installer only provides arm64 builds from Qt 6.7 onwards. Note, Ubuntu (Debian) does provide
+          # arm64 Qt builds, so we don't exclude `5` nor `6`, just the Qt online versions (5.x.y and 6.[0-6].y).
+          - { qt: 5.9.9,   arch: arm64 }
+          - { qt: 5.10.1,  arch: arm64 }
+          - { qt: 5.11.3,  arch: arm64 }
+          - { qt: 5.12.12, arch: arm64 }
+          - { qt: 5.13.2,  arch: arm64 }
+          - { qt: 5.14.2,  arch: arm64 }
+          - { qt: 5.15.2,  arch: arm64 }
+          - { qt: 6.2.4,   arch: arm64 }
+          - { qt: 6.3.2,   arch: arm64 }
+          - { qt: 6.4.3,   arch: arm64 }
+          - { qt: 6.5.3,   arch: arm64 }
+          - { qt: 6.6.3,   arch: arm64 }
     steps:
       - name: Upgrade OS
         run: |