ci: make install_deps.sh more flexible

This will allow us to use it in containers as well as specify whether we
want to install test dependencies.

.github/scripts/install_deps.sh

@@ -1,10 +1,31 @@
 #!/bin/bash
 
+SUDO="sudo"
+
+while (($# > 0)); do
+  case $1 in
+  --test) # install test dependencies
+    TEST=1
+    shift
+    ;;
+  --container) # don't use sudo
+    SUDO=""
+    shift
+    ;;
+  esac
+done
+
 os=$(uname -s)
 if [[ $os == Linux ]]; then
-  sudo apt-get update
-  sudo apt-get install -y build-essential cmake curl gettext locales-all ninja-build pkg-config unzip "$@"
+  $SUDO apt-get update
+  $SUDO apt-get install -y build-essential cmake curl gettext ninja-build pkg-config unzip
+  if [[ -n $TEST ]]; then
+    $SUDO apt-get install -y locales-all cpanminus
+  fi
 elif [[ $os == Darwin ]]; then
   brew update --quiet
-  brew install ninja "$@"
+  brew install ninja
+  if [[ -n $TEST ]]; then
+    brew install cpanminus
+  fi
 fi