Installing package - Warning in system("sh ./") : 'sh' not found

I'm interested in upgrading from R-3.5.0 to R-3.51, and I'm presenting the same problem.
I document what happens to me:

install.packages("stringi", dependencies = TRUE, repos = "")
Installing package into ‘C:/Users/Macabi/Tracing/Documents/R/win-library/3.5’
(as ‘lib’ is unspecified)

  There is a binary version available but the source version is later:
        binary source needs_compilation
stringi  1.1.7  1.2.4              TRUE

installing the source package ‘stringi’

trying URL ''
Content type 'application/x-gzip' length 17916239 bytes (17.1 MB)
downloaded 17.1 MB

* installing *source* package 'stringi' ...
** package 'stringi' successfully unpacked and MD5 sums checked
Warning in system("sh ./") : 'sh' not found
ERROR: configuration failed for package 'stringi'
* removing 'C:/Users/Macabi/Tracing/Documents/R/win-library/3.5/stringi'
Warning in install.packages :
  installation of package ‘stringi’ had non-zero exit status

The downloaded source packages are in
> library(installr)
Loading required package: stringr
Error: package or namespace load failed for ‘stringr’ in loadNamespace(i, c(lib.loc, .libPaths()), versionCheck = vI[[i]]):
 there is no package called ‘stringi’
Error: package ‘stringr’ could not be loaded
In addition: Warning messages:
1: package ‘installr’ was built under R version 3.5.1 
2: package ‘stringr’ was built under R version 3.5.1 

Could you guide me to solve the problem?

Hi Hermes,
I had the same problem as you.
For me, installing the binary package (still version 1.1.7) instead of the source package fixed the problem.
Hope this helps: