Fix build warning on macOs

The aws/tap that ius preinstalled on the macos runner seems to be conflicting... let's ignore it. Here is the warning we're hoping to remove.

The following taps are not trusted:
  aws/tap
Homebrew is currently ignoring formulae, casks and commands from these taps because tap trust is required.
Untap them with:
  brew untap aws/tap
Trust specific formulae, casks and commands with:
  brew trust --formula <user>/<tap>/<formula>
  brew trust --cask <user>/<tap>/<cask>
  brew trust --command <user>/<tap>/<command>
Whole-tap trust is broader and includes all current and future formulae,
casks and commands from the listed taps. Trust whole taps with:
  brew trust aws/tap
To disable trust checks:
  export HOMEBREW_NO_REQUIRE_TAP_TRUST=1
This is not recommended and will be removed in a later release.
For more information, see:
  https://docs.brew.sh/Tap-Trust

.github/workflows/build_viewer.yml

@@ -51,6 +51,10 @@ jobs:
         if: runner.os == 'macOS'
         run: |
           /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
+          # aws/tap is preinstalled on the runner but is not used by this workflow.
+          if brew tap | grep -qx 'aws/tap'; then
+            brew untap aws/tap
+          fi
           brew install bash
           brew install gnu-sed