feat: add borded_cpp benchmark target and switch Dockerfile to gcc

Add borded_cpp_exec to .gitignore, include build_borded_cpp in Makefile all target, and extend bench.py with Borded CPP timing. Change borded_cpp Dockerfile base from alpine to gcc:latest with apt-based dependencies.

borded_cpp/Dockerfile

@@ -1,3 +1,3 @@
-FROM alpine:latest
-RUN apk update && apk add build-base sqlite-dev vim jansson-dev jansson-static cmake
+FROM gcc:latest
+RUN apt update && apt install -y cmake gdb
 WORKDIR /home