Better superenv support for Xcode elsewhere

- The Library/ENV/4.3/xcrun shim now respects
  ENV['DEVELOPER_DIR'] instead assuming the location
  of /Applications/Xcode.app/Contents/Developer.
- The env var DEVELOPER_DIR is set if it is not
  already. So, during superenv this var is always set
  and we no longer have to care about people with unset
  or wrongly set xcode-select stuff. This has been
  a major PITA in the past.
- determine_developer_dir (which is used to set
  the DEVELOPER_DIR var) now uses MacOS::Xcode.prefix
  which is proven and very capable and uses splotlight
  correctly.
- Replace (and remove) MacSystem.xcode43_developer_dir
  with Xcode.prefix

Closes Homebrew/homebrew#18618

Library/ENV/4.3/xcrun

@@ -19,8 +19,8 @@ end
 arg0 = ARGV.shift
 try `/usr/bin/xcrun --find #{arg0}`.chomp
 # Nuts, Xcode is not setup properly or something. Try to find the tools anyway!
-try "/Applications/Xcode.app/Contents/Developer/usr/bin/#{arg0}"
-try "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/#{arg0}"
+try "#{ENV['DEVELOPER_DIR']}/usr/bin/#{arg0}"
+try "#{ENV['DEVELOPER_DIR']}/Toolchains/XcodeDefault.xctoolchain/usr/bin/#{arg0}"
 try "/usr/bin/#{arg0}"
 
 abort <<-EOS

Library/Homebrew/os/mac/xcode.rb

@@ -76,7 +76,7 @@ module MacOS::Xcode extend self
 
     # this shortcut makes version work for people who don't realise you
     # need to install the CLI tools
-    xcode43build = V4_BUNDLE_PATH/'Contents/Developer/usr/bin/xcodebuild'
+    xcode43build = prefix/'usr/bin/xcodebuild'
     if xcode43build.file?
       `#{xcode43build} -version 2>/dev/null` =~ /Xcode (\d(\.\d)*)/
       return $1 if $1

Library/Homebrew/superenv.rb

@@ -18,10 +18,7 @@ end
 
 def superenv?
   not (MacSystem.xcode43_without_clt? and
-    MacOS.sdk_path.nil?) and # because superenv will fail to find stuff
-  not (MacSystem.xcode43_without_clt? and
-    !MacSystem.xcode43_developer_dir) and # because superenv's logic might not find it
-  not MacOS::Xcode.folder.nil? and # because xcrun won't work
+  MacOS.sdk_path.nil?) and # because superenv will fail to find stuff
   superbin and superbin.directory? and
   not ARGV.include? "--env=std"
 rescue # blanket rescue because there are naked raises
@@ -112,8 +109,8 @@ class << ENV
   def determine_path
     paths = [superbin]
     if MacSystem.xcode43_without_clt?
-      paths << "#{MacSystem.xcode43_developer_dir}/usr/bin"
-      paths << "#{MacSystem.xcode43_developer_dir}/Toolchains/XcodeDefault.xctoolchain/usr/bin"
+      paths << "#{MacOS::Xcode.prefix}/usr/bin"
+      paths << "#{MacOS::Xcode.prefix}/Toolchains/XcodeDefault.xctoolchain/usr/bin"
     end
     paths += deps.map{|dep| "#{HOMEBREW_PREFIX}/opt/#{dep}/bin" }
     paths << "#{HOMEBREW_PREFIX}/opt/python/bin" if brewed_python?
@@ -197,11 +194,7 @@ class << ENV
     # If Xcode path is fucked then this is basically a fix. In the case where
     # nothing is valid, it still fixes most usage to supply a valid path that
     # is not "/".
-    if MacOS::Xcode.bad_xcode_select_path?
-      (MacOS::Xcode.prefix || HOMEBREW_PREFIX).to_s
-    elsif ENV['DEVELOPER_DIR']
-      ENV['DEVELOPER_DIR']
-    end
+    MacOS::Xcode.prefix || ENV['DEVELOPER_DIR']
   end
 
   def brewed_python?

Library/Homebrew/superenv/macsystem.rb

 # new code because I don't really trust the Xcode code now having researched it more
 module MacSystem extend self
   def xcode_clt_installed?
-    File.executable? "/usr/bin/clang" and File.executable? "/usr/bin/lldb"
+    File.executable? "/usr/bin/clang" and File.executable? "/usr/bin/lldb" and File.executable? "/usr/bin/make"
   end
 
   def xcode43_without_clt?
@@ -13,16 +13,6 @@ module MacSystem extend self
       #{MacOS.sdk_path}/usr/X11].find{|path| File.directory? "#{path}/include" }
   end
 
-  def xcode43_developer_dir
-    @xcode43_developer_dir ||=
-      tst(ENV['DEVELOPER_DIR']) ||
-      tst(`xcode-select -print-path 2>/dev/null`) ||
-      tst("/Applications/Xcode.app/Contents/Developer") ||
-      MacOS.mdfind("com.apple.dt.Xcode").find{|path| tst(path) }
-    raise unless @xcode43_developer_dir
-    @xcode43_developer_dir
-  end
-
   private
 
   def tst prefix