Patch allow gcc10

[j4qfrost]

Resolves this issue neovide/neovide#306

[j4qfrost]

I haven't had any luck creating a good testing environment with gcc10 with github actions. Anyone want to take a stab at that?

[Cobrand]

if local_ver >= affected_ver {
    cfg.cflag("-fcommon");
    cfg.cflag("-fPIE");
}

Why is this necessary? It seems to be the core of the fix, but we don't know why those two flags are necessary.

For github actions, I have no clue. We were using travis at first, but it broke at some point for some reason, so we need to merge the travis script to github actions or vice-versa, so in the meanwhile it's not really that important I guess.

[j4qfrost]

I'm not totally sure about why adding those flags works, but a number of users for a text editor that I'm supporting ran into a linking issue on systems using gcc 10. I found the suggested fix here onivim/oni2#1778 and have tested adding the cflags locally, and it fixes my issue. Alternatively, the issue can be fixed by simply doing CFLAGS='-fcommon -fPIE' cargo run, so this change isn't entirely necessary.

[Cobrand]

Can you test with only -fcommon without -fPIE? PIE is for Position Independant Executable, and I'm not sure it's useful here (I read that if fixes some issues with dlopen, but we're not using it here so...)

[j4qfrost]

I checked and it works. I think the PIE requirement might be on our side on specific machines.

[Cobrand]

Thanks!