update run_builder, build_sources integration tests for more coverage

build_tests/simple/build_sources.rb

@@ -10,5 +10,13 @@ end
 
 Rscons::Environment.new do |env|
   env.add_builder(MyProgram.new)
-  env.MyProgram("simple.exe", "simple.c")
+  env.Object("simple.o", "simple.c")
+  File.open("two.c", "wb") do |fh|
+    fh.puts <<-EOF
+      void two(void)
+      {
+      }
+    EOF
+  end
+  env.MyProgram("simple.exe", ["simple.o", "two.c"])
 end

spec/build_tests_spec.rb

@@ -647,10 +647,21 @@ EOF
     expect(result.stderr).to eq ""
     expect(lines(result.stdout)).to eq [
       "CC simple.o",
+      "CC two.o",
       "MyProgram simple.exe",
     ]
   end
 
+  it "prints the failed build command for a threaded builder when called via Environment#run_builder without delayed execution" do
+    test_dir("simple")
+    File.open("simple.c", "wb") do |fh|
+      fh.write("FOOBAR")
+    end
+    result = run_test(rsconsfile: "run_builder.rb")
+    expect(result.stderr).to match /Failed to build/
+    expect(result.stdout).to match /Failed command was: gcc/
+  end
+
   context "Directory builder" do
     it "creates the requested directory" do
       test_dir("simple")