support false :use value for configure operations - close #93

build_tests/configure/check_lib_use_false.rb

@@ -0,0 +1,10 @@
+configure do
+  check_lib "m", use: false
+end
+
+build do
+  Environment.new(echo: :command) do |env|
+    env.Copy("test1.c", "simple.c")
+    env.Program("test2.exe", "test1.c")
+  end
+end