Formula#specified_path

Library/Homebrew/formula.rb

@@ -226,6 +226,11 @@ class Formula
 
   public
 
+  # The path that was specified to find/install this formula.
+  def specified_path
+    alias_path || path
+  end
+
   # Is the currently active {SoftwareSpec} a {#stable} build?
   # @private
   def stable?

Library/Homebrew/formula_installer.rb

@@ -589,7 +589,7 @@ class FormulaInstaller
       -I #{HOMEBREW_LOAD_PATH}
       --
       #{HOMEBREW_LIBRARY_PATH}/build.rb
-      #{formula.alias_path || formula.path}
+      #{formula.specified_path}
     ].concat(build_argv)
 
     Sandbox.print_sandbox_message if Sandbox.formula?(formula)