MarkdownReportsDev cannot be installed on older MAC where xcode is not available / why does it even require xcode?

[vertesy]

library(package, lib.loc = lib.loc, character.only = TRUE, logical.return = TRUE,  :
  there is no package called ‘MarkdownReportsDev’
>   devtools::install_github(repo = "vertesy/MarkdownReportsDev")
Downloading GitHub repo vertesy/MarkdownReportsDev@HEAD
✓  checking for file ‘/private/var/folders/c0/r1nv6hvs1h5dzz_xy2b1q9zc001rts/T/RtmpHzKrM6/remotes2f8d7d396ffe/vertesy-MarkdownReportsDev-7b4b718/DESCRIPTION’ ...
─  preparing ‘MarkdownReportsDev’:
✓  checking DESCRIPTION meta-information ...
─  excluding invalid files
   Subdirectory 'man' contains invalid file names:
     ‘MarkdownReportsDev-Ex.pdf’ ‘MarkdownReportsDev-Ex.timings’
     ‘man.log.md’
─  checking for LF line-endings in source and make files and shell scripts
─  checking for empty or unneeded directories
─  building ‘MarkdownReportsDev_4.1.4.tar.gz’
   Warning: invalid uid value replaced by that for user 'nobody'
   
Installing package into ‘/Users/camilla.bosone/Library/R/4.0/library’
(as ‘lib’ is unspecified)
* installing *source* package ‘MarkdownReportsDev’ ...
** using staged installation
** R
** byte-compile and prepare package for lazy loading
xcode-select: note: no developer tools were found at '/Applications/Xcode.app', requesting install. Choose an option in the dialog to download the command line developer tools.
Warning in system2("/usr/bin/otool", c("-L", shQuote(DSO)), stdout = TRUE) :
  running command ''/usr/bin/otool' -L '/Library/Frameworks/R.framework/Resources/library/tcltk/libs//tcltk.so'' had status 1
Error: .onLoad failed in loadNamespace() for 'tcltk', details:
  call: dyn.load(file, DLLpath = DLLpath, ...)
  error: unable to load shared object '/Library/Frameworks/R.framework/Versions/4.0/Resources/library/tcltk/libs/tcltk.so':
  dlopen(/Library/Frameworks/R.framework/Versions/4.0/Resources/library/tcltk/libs/tcltk.so, 10): Library not loaded: /opt/X11/lib/libfontconfig.1.dylib
  Referenced from: /usr/local/lib/libtk8.6.dylib
  Reason: Incompatible library version: libtk8.6.dylib requires version 11.0.0 or later, but libfontconfig.1.dylib provides version 10.0.0
Execution halted
ERROR: lazy loading failed for package ‘MarkdownReportsDev’
* removing ‘/Users/camilla.bosone/Library/R/4.0/library/MarkdownReportsDev’
Error: Failed to install 'MarkdownReportsDev' from GitHub:
  (converted from warning) installation of package ‘/var/folders/c0/r1nv6hvs1h5dzz_xy2b1q9zc001rts/T//RtmpHzKrM6/file2f8d45e7ccec/MarkdownReportsDev_4.1.4.tar.gz’ had non-zero exit status
>   devtools::install_github(repo = "vertesy/MarkdownReportsDev")
Downloading GitHub repo vertesy/MarkdownReportsDev@HEAD
✓  checking for file ‘/private/var/folders/c0/r1nv6hvs1h5dzz_xy2b1q9zc001rts/T/RtmpHzKrM6/remotes2f8d664dfc0/vertesy-MarkdownReportsDev-7b4b718/DESCRIPTION’ ...
─  preparing ‘MarkdownReportsDev’:
✓  checking DESCRIPTION meta-information ...
─  excluding invalid files
   Subdirectory 'man' contains invalid file names:
     ‘MarkdownReportsDev-Ex.pdf’ ‘MarkdownReportsDev-Ex.timings’
     ‘man.log.md’
─  checking for LF line-endings in source and make files and shell scripts
─  checking for empty or unneeded directories
─  building ‘MarkdownReportsDev_4.1.4.tar.gz’
   Warning: invalid uid value replaced by that for user 'nobody'
   
Installing package into ‘/Users/camilla.bosone/Library/R/4.0/library’
(as ‘lib’ is unspecified)
* installing *source* package ‘MarkdownReportsDev’ ...
** using staged installation
** R
** byte-compile and prepare package for lazy loading
xcode-select: note: no developer tools were found at '/Applications/Xcode.app', requesting install. Choose an option in the dialog to download the command line developer tools.
Warning in system2("/usr/bin/otool", c("-L", shQuote(DSO)), stdout = TRUE) :
  running command ''/usr/bin/otool' -L '/Library/Frameworks/R.framework/Resources/library/tcltk/libs//tcltk.so'' had status 1
Error: .onLoad failed in loadNamespace() for 'tcltk', details:
  call: dyn.load(file, DLLpath = DLLpath, ...)
  error: unable to load shared object '/Library/Frameworks/R.framework/Versions/4.0/Resources/library/tcltk/libs/tcltk.so':
  dlopen(/Library/Frameworks/R.framework/Versions/4.0/Resources/library/tcltk/libs/tcltk.so, 10): Library not loaded: /opt/X11/lib/libfontconfig.1.dylib
  Referenced from: /usr/local/lib/libtk8.6.dylib
  Reason: Incompatible library version: libtk8.6.dylib requires version 11.0.0 or later, but libfontconfig.1.dylib provides version 10.0.0
Execution halted
ERROR: lazy loading failed for package ‘MarkdownReportsDev’
* removing ‘/Users/camilla.bosone/Library/R/4.0/library/MarkdownReportsDev’
Error: Failed to install 'MarkdownReportsDev' from GitHub:
  (converted from warning) installation of package ‘/var/folders/c0/r1nv6hvs1h5dzz_xy2b1q9zc001rts/T//RtmpHzKrM6/file2f8d489db987/MarkdownReportsDev_4.1.4.tar.gz’ had non-zero exit status