add configure spec to check multiple set_define's being stored

build_tests/configure/multiple_set_define.rb

@@ -0,0 +1,8 @@
+configure do
+  check_c_header "math.h", set_define: "HAVE_MATH_H"
+  check_c_header "stdio.h", set_define: "HAVE_STDIO_H"
+end
+
+Rscons::Environment.new(echo: :command) do |env|
+  env.Object("simple.o", "simple.c")
+end