add specs testing configure :set_define option and fix the same

build_tests/configure/check_c_header_no_fail_set_define.rb

@@ -0,0 +1,7 @@
+configure do
+  check_c_header "not___found.h", fail: false, set_define: "HAVE_NOT___FOUND_H"
+end
+
+Rscons::Environment.new(echo: :command) do |env|
+  env.Object("simple.o", "simple.c")
+end

build_tests/configure/check_c_header_success_set_define.rb

@@ -0,0 +1,7 @@
+configure do
+  check_c_header "string.h", set_define: "HAVE_STRING_H"
+end
+
+Rscons::Environment.new(echo: :command) do |env|
+  env.Object("simple.o", "simple.c")
+end

lib/rscons/configure_op.rb

@@ -398,6 +398,9 @@ module Rscons
       success_message = options[:success_message] || "found"
       if status == 0
         Ansi.write($stdout, :green, "#{success_message}\n")
+        if options[:set_define]
+          store_append("CPPDEFINES" => options[:set_define])
+        end
       else
         if options.has_key?(:fail) and not options[:fail]
           Ansi.write($stdout, :yellow, "not found\n")
@@ -406,9 +409,6 @@ module Rscons
           raise ConfigureFailure.new
         end
       end
-      if options[:set_define]
-        store_append("CPPDEFINES" => options[:set_define])
-      end
     end
 
     # Check if a directory contains a certain executable.

spec/build_tests_spec.rb

@@ -1659,6 +1659,30 @@ EOF
         expect(result.status).to eq 0
         expect(result.stdout).to match /Checking for C header 'not___found\.h'... not found/
       end
+
+      it "sets the specified define when the header is found" do
+        test_dir "configure"
+        result = run_rscons(rsconscript: "check_c_header_success_set_define.rb", op: "configure")
+        expect(result.stderr).to eq ""
+        expect(result.status).to eq 0
+        expect(result.stdout).to match /Checking for C header 'string\.h'... found/
+        result = run_rscons(rsconscript: "check_c_header_success_set_define.rb", op: "build")
+        expect(result.stderr).to eq ""
+        expect(result.status).to eq 0
+        expect(result.stdout).to match /-DHAVE_STRING_H/
+      end
+
+      it "does not set the specified define when the header is not found" do
+        test_dir "configure"
+        result = run_rscons(rsconscript: "check_c_header_no_fail_set_define.rb", op: "configure")
+        expect(result.stderr).to eq ""
+        expect(result.status).to eq 0
+        expect(result.stdout).to match /Checking for C header 'not___found\.h'... not found/
+        result = run_rscons(rsconscript: "check_c_header_no_fail_set_define.rb", op: "build")
+        expect(result.stderr).to eq ""
+        expect(result.status).to eq 0
+        expect(result.stdout).to_not match /-DHAVE_/
+      end
     end
 
     context "check_cxx_header" do