Moved platform specific code to its own directory.

build.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 mkdir -p build
-pushd build
+pushd build > /dev/null
 rm -rf sdl_platform.dSYM
 
 # Plugin library
@@ -9,5 +9,7 @@ c++ -shared -o librt_weekend.so librt_weekend.o
 rm librt_weekend.o
 
 # Platform layer host application
-c++ -Wall -std=c++11 -g ../code/sdl_platform.cpp -o sdl_platform `sdl2-config --libs --cflags`
-popd
+c++ -Wall -std=c++11 -g ../code/platforms/sdl_platform.cpp -o sdl_platform \
+`sdl2-config --libs --cflags`
+
+popd > /dev/null