allow phony targets in conjunction with a build root

lib/rscons/environment.rb

@@ -509,8 +509,12 @@ module Rscons
     #
     # @return [String] The expanded path.
     def expand_path(path)
+      if Rscons.phony_target?(path)
+        path
+      else
         path.sub(%r{^\^(?=[\\/])}, @build_root)
       end
+    end
 
     # Execute a command using the system shell.
     #

spec/build_tests_spec.rb

@@ -933,9 +933,11 @@ EOF
   end
 
   context "phony targets" do
+    [false, true].each do |with_build_root|
       it "allows specifying a Symbol as a target name and reruns the builder if the sources or command have changed" do
         test_dir("simple")
         env = Rscons::Environment.new do |env|
+          env.build_root = "bld" if with_build_root
           env.add_builder(:Checker) do |target, sources, cache, env, vars|
             unless cache.up_to_date?(target, :Checker, sources, env)
               puts "Checker #{sources.first}" if env.echo != :off
@@ -946,7 +948,7 @@ EOF
           env.Program("simple.exe", "simple.c")
           env.Checker(:checker, "simple.exe")
         end
-      expect(lines).to eq(["CC simple.o", "LD simple.exe", "Checker simple.exe"])
+        expect(lines).to eq(["CC #{with_build_root ? 'bld/' : ''}simple.o", "LD simple.exe", "Checker simple.exe"])
 
         env.clone do |env|
           env.Checker(:checker, "simple.exe")
@@ -962,5 +964,6 @@ EOF
         expect(lines).to eq(["Checker simple.exe"])
       end
     end
+  end
 
 end