(puppetlabs#8660) Fix destdir option on Windows

Specifying the --destdir option failed on windows because the install
script attempted to concatenate two absolute paths together. On Unix,
this is fine, but on Windows, it fails because the colon (part of the
drive specifier) is not a valid filename character. This commit adds a
method to join two paths, stripping off the drive specifier, if
present.

Also fixed a minor bug, which caused a deprecation warning to always
be printed when the --destdir option is omitted, which is the default
case.

Reviewed-by: Cameron Thomas <[email protected]>
(cherry picked from commit f600617)

install.rb

@@ -286,18 +286,18 @@ def prepare_installation
   if not InstallOptions.destdir.nil?
     destdir = InstallOptions.destdir
   # To be deprecated once people move over to using --destdir option
-  elsif ENV['DESTDIR'] != nil?
+  elsif not ENV['DESTDIR'].nil?
     destdir = ENV['DESTDIR']
     warn "DESTDIR is deprecated. Use --destdir instead."
   else
     destdir = ''
   end
 
-  configdir = "#{destdir}#{configdir}"
-  bindir = "#{destdir}#{bindir}"
-  sbindir = "#{destdir}#{sbindir}"
-  mandir = "#{destdir}#{mandir}"
-  sitelibdir = "#{destdir}#{sitelibdir}"
+  configdir = join(destdir, configdir)
+  bindir = join(destdir, bindir)
+  sbindir = join(destdir, sbindir)
+  mandir = join(destdir, mandir)
+  sitelibdir = join(destdir, sitelibdir)
 
   FileUtils.makedirs(configdir) if InstallOptions.configs
   FileUtils.makedirs(bindir)
@@ -316,6 +316,16 @@ def prepare_installation
   InstallOptions.man_dir  = mandir
 end
 
+##
+# Join two paths. On Windows, dir must be converted to a relative path,
+# by stripping the drive letter, but only if the basedir is not empty.
+#
+def join(basedir, dir)
+  return "#{basedir}#{dir[2..-1]}" if $operatingsystem == "windows" and basedir.length > 0 and dir.length > 2
+
+  "#{basedir}#{dir}"
+end
+
 ##
 # Build the rdoc documentation. Also, try to build the RI documentation.
 #