Use pre-existing homebrew state on CircleCI VMs (#2608)

CircleCI VMs come pre-installed with homebrew and some of the taps and packages we need already set up, so skipping running update and tap and install for those pre-existing assets reduces each job by ~6 minutes each (x 4 jobs).

scripts/configure_dev.sh

@@ -72,16 +72,20 @@ if [ "${OS}" = "linux" ]; then
         sudo "$SCRIPTPATH/install_linux_deps.sh"
     fi
 elif [ "${OS}" = "darwin" ]; then
-    brew update
-    brew tap homebrew/cask
+    if [ "${CIRCLECI}" != "true" ]; then
+        brew update
+        brew tap homebrew/cask
+    fi
     install_or_upgrade pkg-config
     install_or_upgrade boost
-    install_or_upgrade jq
     install_or_upgrade libtool
-    install_or_upgrade autoconf
-    install_or_upgrade automake
     install_or_upgrade shellcheck
-    install_or_upgrade python3
+    if [ "${CIRCLECI}" != "true" ]; then
+        install_or_upgrade jq
+        install_or_upgrade autoconf
+        install_or_upgrade automake
+        install_or_upgrade python3
+    fi
 elif [ "${OS}" = "windows" ]; then
     if ! $msys2 pacman -S --disable-download-timeout --noconfirm git automake autoconf m4 libtool make mingw-w64-x86_64-gcc mingw-w64-x86_64-boost mingw-w64-x86_64-python mingw-w64-x86_64-jq unzip procps; then
         echo "Error installing pacman dependencies"

scripts/travis/configure_dev.sh

@@ -21,9 +21,11 @@ if [[ "${OS}" == "linux" ]]; then
 elif [[ "${OS}" == "darwin" ]]; then
     # we don't want to upgrade boost if we already have it, as it will try to update
     # other components.
-    brew update
-    brew tap homebrew/cask
-    brew pin boost || true
+    if [ "${CIRCLECI}" != "true" ]; then
+        brew update
+        brew tap homebrew/cask
+        brew pin boost || true
+    fi
 elif [[ "${OS}" == "windows" ]]; then
     git config --global core.autocrlf true
     # Golang probably is not installed under MSYS2 so add the environment variable temporarily