Error(s) in re-building vignettes:
--- re-building ‘advanced_features.Rmd’ using rmarkdown
dyld: lazy symbol binding failed: Symbol not found: ____chkstk_darwin
  Referenced from: /usr/local/bin/pandoc (which was built for Mac OS X 10.15)
  Expected in: /usr/lib/libSystem.B.dylib

dyld: Symbol not found: ____chkstk_darwin
  Referenced from: /usr/local/bin/pandoc (which was built for Mac OS X 10.15)
  Expected in: /usr/lib/libSystem.B.dylib

Error: processing vignette 'advanced_features.Rmd' failed with diagnostics:
pandoc document conversion failed with error 6
--- failed re-building ‘advanced_features.Rmd’

--- re-building ‘known_issues.Rmd’ using rmarkdown
dyld: lazy symbol binding failed: Symbol not found: ____chkstk_darwin
  Referenced from: /usr/local/bin/pandoc (which was built for Mac OS X 10.15)
  Expected in: /usr/lib/libSystem.B.dylib

dyld: Symbol not found: ____chkstk_darwin
  Referenced from: /usr/local/bin/pandoc (which was built for Mac OS X 10.15)
  Expected in: /usr/lib/libSystem.B.dylib

Error: processing vignette 'known_issues.Rmd' failed with diagnostics:
pandoc document conversion failed with error 6
--- failed re-building ‘known_issues.Rmd’

--- re-building ‘opentripplanner.Rmd’ using rmarkdown
dyld: lazy symbol binding failed: Symbol not found: ____chkstk_darwin
  Referenced from: /usr/local/bin/pandoc (which was built for Mac OS X 10.15)
  Expected in: /usr/lib/libSystem.B.dylib

dyld: Symbol not found: ____chkstk_darwin
  Referenced from: /usr/local/bin/pandoc (which was built for Mac OS X 10.15)
  Expected in: /usr/lib/libSystem.B.dylib

Error: processing vignette 'opentripplanner.Rmd' failed with diagnostics:
pandoc document conversion failed with error 6
--- failed re-building ‘opentripplanner.Rmd’

--- re-building ‘prerequisites.Rmd’ using rmarkdown
Warning in get_engine(options$engine) :
  Unknown language engine 'eval' (must be registered via knit_engines$set()).
dyld: lazy symbol binding failed: Symbol not found: ____chkstk_darwin
  Referenced from: /usr/local/bin/pandoc (which was built for Mac OS X 10.15)
  Expected in: /usr/lib/libSystem.B.dylib

dyld: Symbol not found: ____chkstk_darwin
  Referenced from: /usr/local/bin/pandoc (which was built for Mac OS X 10.15)
  Expected in: /usr/lib/libSystem.B.dylib

Error: processing vignette 'prerequisites.Rmd' failed with diagnostics:
pandoc document conversion failed with error 6
--- failed re-building ‘prerequisites.Rmd’

SUMMARY: processing the following files failed:
  ‘advanced_features.Rmd’ ‘known_issues.Rmd’ ‘opentripplanner.Rmd’
  ‘prerequisites.Rmd’

Error: Vignette re-building failed.
Execution halted