cmake-ing is ridiculously slow and stalls on -- Getting container node sizes

[lewardo]

running cmake stalls for ~5 minutes on -- Getting container node sizes every time it is run

@tremblap remembers it's something apropos checking dependencies on remote sources and mentioned a fabled, convoluted cmake incantation that would skip the checks but can't remember

[tremblap]

foonathan/memory#143 seems to 'sort' it but I never got it to work

[jamesb93]

I have experienced this also...

[AlexHarker]

Me too

[weefuzzy]

As it stands it should only need be slow on first invocation, unless people are junking their cmake output between runs (?). I don't think we need the header, so we could pre-generate to spoof if necessary.