reduce duplicated paths in docs

Author: jameslamb

R-package/README.md

@@ -35,10 +35,7 @@ After installing `Rtools` and `CMake`, be sure the following paths are added to
 * `R`
     - example: `C:\Program Files\R\R-3.6.1\bin`
 
-As of `Rtools` 4.0, some common paths changed and software was removed from `Rtools`. If you are using `R` 4.0 or later and the corresponding `Rtools`, you need to add one additional path to `PATH`.
-
-* `Rtools` usr bin:
-    - example: `C:\Rtools\usr\bin`
+NOTE: Two `Rtools` paths are required from `Rtools` 4.0 onwards because paths and the list of included software was changed in `Rtools` 4.0.
 
 #### Windows Toolchain Options
 

R-package/inst/make-r-def.R

@@ -41,9 +41,12 @@ message(sprintf("Creating '%s' from '%s'", OUT_DEF_FILE, IN_DLL_FILE))
           , "'processx' with install.packages('processx') might "
           , "make this faster."
         ))
+        # shQuote() is necessary here since one of the arguments
+        # is a file-path to R.dll, which may have spaces. processx
+        # does such quoting but system2() does not
         exit_code <- system2(
             command = command
-            , args = args
+            , args = shoQuote(args)
             , stdout = out_file
         )
         if (exit_code != 0L) {