ci: install dependencies with a single script (#22241)

It's easier if the os-specific installations are done by the script itself

.github/scripts/install_dependencies.cmake

@@ -0,0 +1,27 @@
+cmake_minimum_required(VERSION 3.10)
+
+if(APPLE)
+  execute_process(COMMAND brew update --quiet)
+  execute_process(COMMAND brew install automake ninja)
+  if(TEST_DEPS)
+    execute_process(COMMAND brew install cpanminus)
+  endif()
+else()
+  # Assuming ubuntu for now. May expand if required.
+  set(PACKAGES
+    autoconf
+    automake
+    build-essential
+    curl
+    gettext
+    libtool-bin
+    locales-all
+    ninja-build
+    pkg-config
+    unzip)
+  execute_process(COMMAND sudo apt-get update)
+  execute_process(COMMAND sudo apt-get install -y ${PACKAGES})
+  if(TEST_DEPS)
+    execute_process(COMMAND sudo apt-get install -y cpanminus)
+  endif()
+endif()

.github/scripts/install_deps_ubuntu.sh

@@ -1,19 +0,0 @@
-#!/bin/bash
-
-PACKAGES=(
-  autoconf
-  automake
-  build-essential
-  cmake
-  cpanminus
-  curl
-  gettext
-  libtool-bin
-  locales-all
-  ninja-build
-  pkg-config
-  unzip
-)
-
-sudo apt-get update
-sudo apt-get install -y "${PACKAGES[@]}"