libs found with check_lib should be added to LIBS - close #79

build_tests/configure/check_lib_success.rb

@@ -1,3 +1,9 @@
 configure do
   check_lib "m"
 end
+
+build do
+  Environment.new(echo: :command) do |env|
+    env.Program("simple.exe", "simple.c")
+  end
+end