Park resolutions to common build problems in FAQ (#9472)
* Proposal to put resolutions to common build problems somewhere. Could be in the already-overloaded FAQ?
* Add paragraph-level headlines, tweak the language to be less finger-pointing add user
* Consolidate with the final resolution found to "Repository not found." error
* Apply suggestions from @agjohnson code review
Co-authored-by: Anthony <aj@ohess.org>
* Create new section Build Troubleshooting, expand explanation about adding deploy keys
Co-authored-by: Anthony <aj@ohess.org>