missing --vanilla option in INSTALL (PR#9877)

Full_Name: Vilmos Prokaj
Version: 2.5.1
OS: windows
Submission from: (NULL) (81.183.3.216)


I'm not sure that this is really a bug, if not I do not understand why 
should it be in this way.

Most of the scripts used to build and install new packages calls the R 
program with the --slave --vanilla command line options.

In the INSTALL script however we can find the following lines


if($opt_library){
   # remove quotes around the library path
   $opt_library =~ s/^['"]//; $opt_library =~ s/['"]$//; #'"
   chdir($opt_library) ||
	die "Error: cannot change to library directory \$opt_library'\n";
   $library = cwd();
   $library = Win32::GetShortPathName($library) if $library =~ / /;
   my $R_LIBS = $ENV{'R_LIBS'};
   $ENV{'R_LIBS'} = join(";", $library, $R_LIBS);
   chdir($startdir);
} else {
   my @out = R_runR("cat('\n~~~', .libPaths()[1], '\n', sep = '')",
"--slave");
   foreach $f (@out) {
	if($f =~ /^~~~/) {
	    $library = $f;
	    $library =~ s/^~~~//;
	}
   }
   $library = Win32::GetShortPathName($library) if $library =~ / /;
   print "installing to '$library'\n";
}

I think that in the R_runR function there should be also a --vanilla option,
otherwise the process might be slow depending on the content of  .Rprofile
file.

The linenumber of the critical point is 132.

Sincerely yours
 Vilmos Prokaj