GHActions: Don't update homebrew when not necessary

It's pretty slow and if GH hasn't been updating their image, could cause huge numbers of extra dependants and dependencies to have to be installed

.github/workflows/macos-workflow.yml

@@ -99,8 +99,14 @@ jobs:
           HOMEBREW_NO_INSTALL_CLEANUP: 1
           HOMEBREW_NO_ANALYTICS: 1
         run: |
-          brew update
-          brew install sound-touch portaudio wxmac gtk+3 sdl2 libsamplerate
+          # To save time, only brew update if running the install without it fails
+          function do-install() {
+            brew install sound-touch portaudio wxmac gtk+3 sdl2 libsamplerate
+          }
+          if ! do-install; then
+            brew update
+            do-install
+          fi
 
       - name: Generate CMake Files
         run: cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_BUILD_PO=FALSE -B build .