This reminds of IGCC (interactive GCC) [1] which I forked from [2] some time ago and since then I try to maintain it.
I don't use it very often, but it's handy to try out syntax or certain snippets. At its core, it continuously updates a temporary file that gets sent to gcc for compilation. Flags & libs can be specified in a config.
[1] https://github.com/alexandru-dinu/igcc
[2] https://sourceforge.net/projects/igcc/