[TravisCI] Add scripts to build and test Z3 on macOS (OSX) and

add a single configuration to TravisCI to test.

TravisCI is very slow at running macOS jobs so just have one
configuration for now.

contrib/ci/scripts/install_deps_osx.sh

@@ -0,0 +1,47 @@
+#!/bin/bash
+
+SCRIPT_DIR="$( cd ${BASH_SOURCE[0]%/*} ; echo $PWD )"
+. ${SCRIPT_DIR}/run_quiet.sh
+
+set -x
+set -e
+set -o pipefail
+
+run_quiet brew update
+export HOMEBREW_NO_AUTO_UPDATE=1
+
+function brew_install_or_upgrade() {
+  if brew ls --versions "$1" > /dev/null 2>&1 ; then
+    brew upgrade "$1"
+  else
+    brew install "$1"
+  fi
+}
+
+# FIXME: We should fix the versions of dependencies used
+# so that we have reproducible builds.
+
+# HACK: Just use CMake version in TravisCI for now
+if [ "X${MACOS_UPDATE_CMAKE}" = "X1" ]; then
+  brew_install_or_upgrade cmake
+fi
+
+if [ "X${Z3_CMAKE_GENERATOR}" = "XNinja" ]; then
+  brew_install_or_upgrade ninja
+fi
+
+if [ "X${USE_LIBGMP}" = "X1" ]; then
+  brew_install_or_upgrade gmp
+fi
+
+if [ "X${BUILD_DOCS}" = "X1" ]; then
+  brew_install_or_upgrade doxygen
+fi
+
+if [ "X${DOTNET_BINDINGS}" = "X1" ]; then
+  brew_install_or_upgrade mono
+fi
+
+if [ "X${JAVA_BINDINGS}" = "X1" ]; then
+  brew cask install java
+fi