add catch2 package (#74)

catch2/build.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+set -e
+
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null && pwd)"
+cd "$DIR"
+
+VERSION="v2.13.10"
+INSTALL_DIR="$DIR/catch2/install"
+
+if [ ! -d "catch2-src/.git" ]; then
+  rm -rf catch2-src
+  git clone --depth 1 https://github.com/catchorg/Catch2.git catch2-src
+fi
+git -C catch2-src fetch --depth 1 origin "$VERSION"
+git -C catch2-src checkout --force FETCH_HEAD
+
+rm -rf "$INSTALL_DIR"
+mkdir -p "$INSTALL_DIR/include"
+cp -r catch2-src/single_include/catch2 "$INSTALL_DIR/include/"
+
+echo "Installed catch2 to $INSTALL_DIR"
+du -sh "$INSTALL_DIR"