Fix Homebrew/homebrew#13012 properly and don't set the SDK if CLT

Undoing parts of the hot fix 78b9e8548e771a59e382e6f13339664ec5498391.

The only thing missing was to check for `system "/usr/bin/xcrun -find make 1>/dev/null 2>&1"`
and then it's safe to call locate.

This commit restores the original functionality but without the risk for recursion
and improves the logic of `MacOS.locate`. See below.

To important changes in this commit:

- For Xcode _and_ CLT: don't add the SDK and leave things as before.
So if `MacOS.clt_installed?`, then no `SDKROOT` and `-L` and `-I`
directories are set in `ENV.macosxsdk`.

- Improved the logic for `MacOS.locate` for Xcode-only situations
by assuring that the xcode-select path is correct. This is done
by checking that `bin/make` exists and is executable. Otherwise it
was possible to set xcode-select to an empty dir.
This check is done in `MacOS.sdk_path` too.
We are now able to use Xcode wherever it is and can work even, if
xcode-select is set to invalid values. (Remember some users don't
have sudo access and that is needed to fix xcode-select).

Some minor whitespace fixes.
Minor backtick fix in doctor.rb's printout.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Library/Homebrew/cmd/doctor.rb

@@ -210,7 +210,7 @@ def check_for_broken_symlinks
     end
   end
   unless broken_symlinks.empty? then <<-EOS.undent
-    Broken symlinks were found. Remove them with `brew prune':
+    Broken symlinks were found. Remove them with `brew prune`:
       #{broken_symlinks * "\n      "}
     EOS
   end

Library/Homebrew/extend/ENV.rb

@@ -231,7 +231,7 @@ Please take one of the following actions:
     remove 'CPPFLAGS', "-isystem #{HOMEBREW_PREFIX}/include"
     remove 'LDFLAGS', "-L#{HOMEBREW_PREFIX}/lib"
     sdk = MacOS.sdk_path(v)
-    unless sdk.nil?
+    unless sdk.nil? or MacOS.clt_installed?
       self['SDKROOT'] = nil
       remove 'CPPFLAGS', "-isysroot #{sdk}"
       remove 'CPPFLAGS', "-isystem #{sdk}/usr/include"
@@ -262,7 +262,7 @@ Please take one of the following actions:
     append 'CPPFLAGS', "-isystem #{HOMEBREW_PREFIX}/include"
     prepend 'LDFLAGS', "-L#{HOMEBREW_PREFIX}/lib"
     sdk = MacOS.sdk_path(v)
-    unless sdk.nil?
+    unless sdk.nil? or MacOS.clt_installed?
       # Extra setup to support Xcode 4.3+ without CLT.
       self['SDKROOT'] = sdk
       # Teach the preprocessor and compiler (some don't respect CPPFLAGS)

Library/Homebrew/utils.rb

@@ -298,34 +298,34 @@ module MacOS extend self
     return @locate_cache[tool] if @locate_cache.has_key? tool
 
     if File.executable? "/usr/bin/#{tool}"
+      # Always prefer the unix style.
       path = Pathname.new "/usr/bin/#{tool}"
-    elsif not MacOS.xctools_fucked? and system "/usr/bin/xcrun -find #{tool} 1>/dev/null 2>&1"
-      # xcrun was provided first with Xcode 4.3 and allows us to proxy
-      # tool usage thus avoiding various bugs
-      p = `/usr/bin/xcrun -find #{tool}`.chomp
-      if File.executable?  p
+    else
+      # Xcrun was provided first with Xcode 4.3 and allows us to proxy
+      # tool usage thus avoiding various bugs.
+      p = `/usr/bin/xcrun -find #{tool} 2>/dev/null`.chomp unless MacOS.xctools_fucked?
+      if !p.nil? and !p.empty? and File.executable? p
         path = Pathname.new p
       else
-        path = nil
-      end
-    else
-      # otherwise lets try and figure it out ourselves
+        # This is for the use-case where xcode-select is not set up correctly
+        # with Xcode 4.3+. The tools in Xcode 4.3+ are split over two locations,
+        # usually xcrun would figure that out for us, but it won't work if
+        # xcode-select is not configured properly.
         p = "#{MacOS.dev_tools_path}/#{tool}"
         if File.executable? p
           path = Pathname.new p
         else
-        # This is for the use-case where xcode-select is not set up with
-        # Xcode 4.3+. The tools in Xcode 4.3+ are split over two locations,
-        # usually xcrun would figure that out for us, but it won't work if
-        # xcode-select is not configured properly (i.e. xctools_fucked?).
-        p = "#{MacOS.xcode_prefix}/Toolchains/XcodeDefault.xctoolchain/usr/bin/#{tool}"
+          # Otherwise lets look in the second location.
+          p = "#{MacOS.xctoolchain_path}/usr/bin/#{tool}"
           if File.executable? p
             path = Pathname.new p
           else
+            # We digged so deep but all is lost now.
             path = nil
           end
         end
       end
+    end
     @locate_cache[tool] = path
     return path
   end
@@ -334,14 +334,18 @@ module MacOS extend self
     @dev_tools_path ||= if File.exist? "/usr/bin/cc" and File.exist? "/usr/bin/make"
       # probably a safe enough assumption (the unix way)
       Pathname.new "/usr/bin"
+    elsif not xctools_fucked? and system "/usr/bin/xcrun -find make 1>/dev/null 2>&1"
+      # Wherever "make" is there are the dev tools.
+      # The new way of finding stuff via locate.
+      Pathname.new(`/usr/bin/xcrun -find make`.chomp).dirname
     elsif File.exist? "#{xcode_prefix}/usr/bin/make"
       # cc stopped existing with Xcode 4.3, there are c89 and c99 options though
       Pathname.new "#{xcode_prefix}/usr/bin"
     else
-      # yes this seems dumb, but we can't throw because the existance of
-      # dev tools is not mandatory for installing formula. Eventually we
-      # should make formula specify if they need dev tools or not.
-      Pathname.new "/usr/bin"
+      # Since we are pretty unrelenting in finding Xcode no matter where
+      # it hides, we can now throw in the towel.
+      opoo "You really should consult the `brew doctor`!"
+      ""
     end
   end
 
@@ -361,7 +365,8 @@ module MacOS extend self
 
   def sdk_path(v=MacOS.version)
     # The path of the MacOSX SDK.
-    if !MacOS.xctools_fucked? and File.directory? `xcode-select -print-path 2>/dev/null`.chomp
+    p = `xcode-select -print-path 2>/dev/null`.chomp
+    if !MacOS.xctools_fucked? and File.executable? "#{p}/usr/bin/make"
       path = `#{locate('xcodebuild')} -version -sdk macosx#{v} Path 2>/dev/null`.strip
     elsif File.directory? '/Developer/SDKs/MacOS#{v}.sdk'
       # the old default (or wild wild west style)
@@ -423,13 +428,13 @@ module MacOS extend self
     @xcode_prefix ||= begin
       path = `/usr/bin/xcode-select -print-path 2>/dev/null`.chomp
       path = Pathname.new path
-      if $?.success? and path.directory? and path.absolute?
+      if $?.success? and path.absolute? and File.executable? "#{path}/usr/bin/make"
         path
-      elsif File.directory? '/Developer'
+      elsif File.executable? '/Developer/usr/bin/make'
         # we do this to support cowboys who insist on installing
         # only a subset of Xcode
         Pathname.new '/Developer'
-      elsif File.directory? '/Applications/Xcode.app/Contents/Developer'
+      elsif File.executable? '/Applications/Xcode.app/Contents/Developer/usr/bin/make'
         # fallback for broken Xcode 4.3 installs
         Pathname.new '/Applications/Xcode.app/Contents/Developer'
       else
@@ -442,10 +447,10 @@ module MacOS extend self
           path = `mdfind "kMDItemCFBundleIdentifier == 'com.apple.Xcode'"`.strip
         end
         path = "#{path}/Contents/Developer"
-        if path.empty? or not File.directory? path
-          nil
-        else
+        if !path.empty? and File.executable? "#{path}/usr/bin/make"
           Pathname.new path
+        else
+          nil
         end
       end
     end