PKGBUILD-rubygem: set binary directory

Add option to set the directory for gem binaries to /usr/bin.
Suggested-by: talki walki <lolilolicon@gmail.com>
Signed-off-by: matt mooney <mfm@muteddisk.com>

prototypes/PKGBUILD-rubygem.proto

@@ -26,7 +26,8 @@ package() {
   # makepkg will exit with an error when sourcing the PKGBUILD
   local _gemdir="$(ruby -rubygems -e'puts Gem.default_dir')"
 
-  gem install --ignore-dependencies -i "$pkgdir$_gemdir" "GEMNAME-$pkgver.gem"
+  gem install --ignore-dependencies -i "$pkgdir$_gemdir" -n "$pkgdir/usr/bin" \
+    "GEMNAME-$pkgver.gem"
 }
 
 # vim:set ts=2 sw=2 et: