Error(s) in re-building vignettes:
  ...
--- re-building ‘plot_design_optimization.Rmd’ using rmarkdown
Warning in in_dir(input_dir(), expr) :
  You changed the working directory to /home/hornik/tmp/R.check/r-devel-gcc/Work/build/Packages/FORTLS/data (probably via setwd()). It will be restored to /home/hornik/tmp/R.check/r-devel-gcc/Work/PKGS/FORTLS.Rcheck/vign_test/FORTLS/vignettes. See the Note section in ?knitr::knit
--- finished re-building ‘plot_design_optimization.Rmd’

--- re-building ‘stand_level.Rmd’ using rmarkdown
Warning in in_dir(input_dir(), expr) :
  You changed the working directory to /home/hornik/tmp/R.check/r-devel-gcc/Work/build/Packages/FORTLS/data (probably via setwd()). It will be restored to /home/hornik/tmp/R.check/r-devel-gcc/Work/PKGS/FORTLS.Rcheck/vign_test/FORTLS/vignettes. See the Note section in ?knitr::knit
--- finished re-building ‘stand_level.Rmd’

--- re-building ‘tree_level.Rmd’ using rmarkdown
trying URL ‘https://www.dropbox.com/s/17yl25pbrapat52/Galicia_single_scan_red.laz?dl=1’
Content type 'application/binary' length 15659081 bytes (14.9 MB)
==================================================
downloaded 14.9 MB

trying URL ‘https://www.dropbox.com/s/i905wj0lavklczb/Galicia_multi_scan_red.laz?dl=1’
Content type 'application/binary' length 16353887 bytes (15.6 MB)
==================================================
downloaded 15.6 MB

trying URL ‘https://www.dropbox.com/s/qrps8om12tzi2a1/Rioja_1_red.laz?dl=1’
Content type 'application/binary' length 8964987 bytes (8.5 MB)
==================================================
downloaded 8.5 MB

trying URL ‘https://www.dropbox.com/s/vgau7yy1rezvn2d/Rioja_2_red.laz?dl=1’
Content type 'application/binary' length 8622979 bytes (8.2 MB)
==================================================
downloaded 8.2 MB

Quitting from lines 117-127 (tree_level.Rmd) 
Error: processing vignette ‘tree_level.Rmd’ failed with diagnostics:
DLL requires the use of native symbols
--- failed re-building ‘tree_level.Rmd’

SUMMARY: processing the following file failed:
  ‘tree_level.Rmd’

Error: Vignette re-building failed.
Execution halted