htmltools build crashes compiler

For some time now, I get an error trying to install htmtools 5.1. from source. This is Windows, using a vanilla R command line (to avoid interactions with RStudio). Installation of the stable binary version 5.0 from CRAN works ok. I work a lot with rstan, so I am sure my C++ chain is reasonable. 24 GB Memory should also be enough.

> library(devtools)                                                                                                                                                      
Lade nötiges Paket: usethis                                                                                                                                              
> devtools::install_github("rstudio/htmltools")                                                                                                                          
Using github PAT from envvar GITHUB_PAT                                                                                                                                  
Downloading GitHub repo rstudio/htmltools@HEAD                                                                                                                           
v  checking for file 'C:\Users\Dieter\AppData\Local\Temp\Rtmp0sjupl\remotes31e4209dfa3\rstudio-htmltools-e7f0393/DESCRIPTION' (431ms)                                    
-  preparing 'htmltools':                                                                                                                                                
v  checking DESCRIPTION meta-information ...                                                                                                                             
-  cleaning src                                                                                                                                                          
-  checking for LF line-endings in source and make files and shell scripts (459ms)                                                                                       
-  checking for empty or unneeded directories                                                                                                                            
-  building 'htmltools_0.5.1.9000.tar.gz'                                                                                                                                
                                                                                                                                                                         
* installing *source* package 'htmltools' ...                                                                                                                            
** using staged installation                                                                                                                                             
** libs                                                                                                                                                                  
"C:/rtools40/mingw64/bin/"gcc  -I"C:/R/include" -DNDEBUG          -O2 -Wall  -std=gnu99 -mfpmath=sse -msse2 -mstackrealign -c init.c -o init.o                           
"C:/rtools40/mingw64/bin/"gcc  -I"C:/R/include" -DNDEBUG          -O2 -Wall  -std=gnu99 -mfpmath=sse -msse2 -mstackrealign -c template.c -o template.o                   
Exception: STATUS_ACCESS_VIOLATION at rip=001800A5BFD                                                                                                                    
rax=0000000000030000 rbx=0000000000000002 rcx=000000018031FEF0                                                                                                           
rdx=0000000000410000 rsi=000000018031FF18 rdi=00000001005CF86C                                                                                                           
r8 =00000000FFFFC89C r9 =0000000000000000 r10=0000000100000000                                                                                                           
r11=0000000100429FB2 r12=00000000FFFFC930 r13=000000018031FEF0                                                                                                           
r14=00000000FFFFCC80 r15=0000000180320688                                                                                                                                
rbp=000000000000002D rsp=00000000FFFFC810                                                                                                                                
program=C:\rtools40\usr\bin\sh.exe, pid 279, thread main                                                                                                                 
cs=0033 ds=002B es=002B fs=0053 gs=002B ss=002B                                                                                                                          
make: *** [C:/R/etc/x64/Makeconf:222: template.o] Segmentation fault (core dumped)                                                                                       
make: *** Waiting for unfinished jobs....                                                                                                                                
make: *** [C:/R/etc/x64/Makeconf:222: init.o] Segmentation fault (core dumped)                                                                                           
ERROR: compilation failed for package 'htmltools'                                                                                                                        
* removing 'C:/R/library/htmltools'                                                                                                                                      
* restoring previous 'C:/R/library/htmltools'                                                                                                                            
Warnmeldungen:                                                                                                                                                           
1: In untar2(tarfile, files, list, exdir, restore_times) :                                                                                                               
  skipping pax global extended headers                                                                                                                                   
2: In untar2(tarfile, files, list, exdir, restore_times) :                                                                                                               
  skipping pax global extended headers                                                                                                                                   
3: In i.p(...) :                                                                                                                                                         
  installation of package 'C:/Users/Dieter/AppData/Local/Temp/Rtmp0sjupl/file31e4cc34f/htmltools_0.5.1.9000.tar.gz' had non-zero exit status                             
> install.packages("https://cran.r-project.org/bin/macosx/contrib/4.0/htmltool$