add Library default builder

build_tests/library/build.rb

@@ -0,0 +1,4 @@
+Rscons::Environment.new(echo: :command) do |env|
+  env.Program('library', ['lib.a', 'three.c'])
+  env.Library("lib.a", ['one.c', 'two.c'], 'CPPFLAGS' => ['-Dmake_lib'])
+end

build_tests/library/one.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+#ifdef make_lib
+int main(int argc, char *argv[])
+{
+    printf("Library\n");
+}
+#endif