Extract build-time stdlib check to a method

Library/Homebrew/build.rb

@@ -163,7 +163,23 @@ class Build
 
         begin
           f.install
+          stdlibs = detect_stdlibs
+          Tab.create(f, ENV.compiler, stdlibs.first, f.build).write
+        rescue Exception => e
+          if ARGV.debug?
+            debrew e, f
+          else
+            raise e
+          end
+        end
 
+        # Find and link metafiles
+        f.prefix.install_metafiles Pathname.pwd
+      end
+    end
+  end
+
+  def detect_stdlibs
     keg = Keg.new(f.prefix)
     # This first test includes executables because we still
     # want to record the stdlib for something that installs no
@@ -185,20 +201,6 @@ class Build
     # and dylibs against libc++, libc++-only dependencies can safely
     # link against it.
     stdlibs = keg.detect_cxx_stdlibs :skip_executables => true
-
-          Tab.create(f, ENV.compiler, stdlibs.first, f.build).write
-        rescue Exception => e
-          if ARGV.debug?
-            debrew e, f
-          else
-            raise e
-          end
-        end
-
-        # Find and link metafiles
-        f.prefix.install_metafiles Pathname.pwd
-      end
-    end
   end
 
   def fixopt f