Cast deps to formula before passing them to superenv

Dependency names retain the "tap prefix", e.g. the "homebrew/dupes"
part of "homebrew/dupes/zlib". However formula objects do not, and this
is desired because we do not record the tap name as part of the
installation prefix.

So we need to ensure the correct dep names are passed to superenv,
otherwise it will not add the correct directories to various environment
variables.

Library/Homebrew/build.rb

@@ -108,14 +108,14 @@ class Build
     pre_superenv_hacks
     require 'superenv'
 
-    deps.each do |dep|
+    deps.map(&:to_formula).each do |dep|
       opt = HOMEBREW_PREFIX/:opt/dep
-      fixopt(dep.to_formula) unless opt.directory? or ARGV.ignore_deps?
+      fixopt(dep) unless opt.directory? or ARGV.ignore_deps?
     end
 
     if superenv?
       ENV.keg_only_deps = keg_only_deps.map(&:to_s)
-      ENV.deps = deps.map(&:to_s)
+      ENV.deps = deps.map { |d| d.to_formula.to_s }
       ENV.x11 = reqs.any? { |rq| rq.kind_of?(X11Dependency) }
       ENV.setup_build_environment
       post_superenv_hacks