Add github workflow to run RScons tests

Fix up some macOS test cases

build_tests/two_sources/assuffix.rb

@@ -3,5 +3,5 @@ env do |env|
   env["CFLAGS"] += %w[-S]
   env.Object("one.ssss", "one.c", "CPPFLAGS" => ["-DONE"])
   env.Object("two.sss", "two.c")
-  env.Program("two_sources.exe", %w[one.ssss two.sss], "ASFLAGS" => env["ASFLAGS"] + %w[-x assembler])
+  env.Program("two_sources.exe", %w[one.ssss two.sss], "ASFLAGS" => env["ASFLAGS"] + %w[-x assembler-with-cpp])
 end