Expecting go, cargo, rust and pandoc to build was radical

(as well as their dependents like ripgrep or gh).
They are broken for much newer systems even on x86.
Pandoc may be buildable, some older version of it, which is compatible with ghc 7.x (assuming that builds, to begin with). Haskell is a pain in the bottom generally, and fixing this will probably be non-trivial.
Unless you really need something which strictly requires pandoc, it is likely better to find a suitable replacement for its functionality. There are some apps in normal languages which do something pretty similar. (I have just used such replacement with rb-rtfm-filemanager, worked good enough for the purpose.)
The rest should work, this or that way, i.e. either with some fixes or fallbacks.
P. S. Emacs is weird, and I don’t understand its failures. For example, both release and devel subports fail to build for me on 10.6.8 with a bus error during the bootstrap, however both build fine on 10a190, and I have no idea why that is the case. (Pre-built apps from 10a190 work on 10.6.8, thankfully, but hey…)