Provide support for Rtools 4.0

[jimhester]

No description provided.

[bgoodri]

This PR is not quite working for me. I have R-testing and rtools40 installed in their default locations. At one point, I had beta-2 of rtools40 and then I uninstalled it through Control Panel to then install beta-5 with the default installation options. I also have the 3.5 versions of R and Rtools, although that should not matter. And I have installed pkgbuild at bde0758 . Now I get:

> library(pkgbuild)
> packageVersion("pkgbuild")
[1] ‘1.0.0.9000’
> stopifnot(has_build_tools(debug = TRUE))
Scanning R CMD config CC...
cc_path: /mingw64/bin/gcc 
'/mingw64/bin/gcc.exe' does not exist
Scanning path...
ls: C:\rtools40\usr\bin\ls.exe 
gcc_path: c:\Rtools\mingw_64\bin\gcc.exe 
Scanning registry...
Found C:/Rtools for 3.5 
Found C:/rtools40 for 4.0 
WARNING: Rtools is required to build R packages, but the version of Rtools previously installed in C:/rtools40 has been deleted.

Please download and install Rtools 4.0 from http://cran.r-project.org/bin/windows/Rtools/.
Error: has_build_tools(debug = TRUE) is not TRUE

But C:/rtools40 is definitely present

> dir(file.path("C:", "rtools40"))
 [1] "autorebase.bat"        "autorebasebase1st.bat" "dev"                   "etc"                   "home"                  "mingw32"              
 [7] "mingw32.exe"           "mingw32.ini"           "mingw64"               "mingw64.exe"           "mingw64.ini"           "msys2.exe"            
[13] "msys2.ico"             "msys2.ini"             "msys2_shell.cmd"       "opt"                   "tmp"                   "unins000.dat"         
[19] "unins000.exe"          "usr"  

and this works

> system2(file.path(R.home("bin"), "Rcmd.exe"), "config CC")
/mingw64/bin/gcc

so it seems as if there is some confusion in scanning the registry.

> sessionInfo()
R version 3.6.0 Under development (Testing Rtools) (2018-09-22 r75352)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

Matrix products: default

locale:
[1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252    LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                           LC_TIME=English_United States.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] pkgbuild_1.0.0.9000

loaded via a namespace (and not attached):
[1] processx_3.2.0   compiler_3.6.0   assertthat_0.2.0 R6_2.3.0         base64enc_0.1-3  crayon_1.3.4     callr_3.0.0      ps_1.2.1        

[jimhester]

You also need to add additional files to the rtools directorory as mentioned in #40 (comment)

I needed to add the Rtools.txt and appropriate VERSION.txt files so that the pkgbuild detection would work.

[bgoodri]

OK, like you suggested, I can make this work with a

cat("Rtools version 4.0.0", file = file.path("C:", "rtools40", "VERSION.txt"), sep = "\n")

Thanks!