add initial main.cc and Rsconsfile

Rsconsfile

@@ -0,0 +1,6 @@
+Rscons::Environment.new do |env|
+  sources = Dir["**/*.cc"]
+  env.parse_flags!("!pkg-config --cflags --libs Qt5Core Qt5Gui Qt5Widgets")
+  env.parse_flags!("-fPIE")
+  env.Program("app", sources)
+end