Make Qmake copy res directory instead of OS scripts

Since Qt 5.6 Qmake has supported the (undocumented) file_copies
function.

Moving to an OS independent version is superior for obvious
reasons.

Use in
https://stackoverflow.com/questions/3984104/qmake-how-to-copy-a-file-to-the-output/54162789#54162789

Uses the same interface as the INSTALLS function described here
https://doc.qt.io/qt-5/qmake-advanced-usage.html#installing-files

Implemented in the file_copies.prf file found here
https://code.qt.io/cgit/qt/qtbase.git/log/mkspecs/features/file_copies.prf

build_scripts/win/build.py

@@ -127,9 +127,6 @@ def deploy():
     copy_file(get_project_dir() + "\\third-party\\openvr\\LICENSE", get_deploy_dir() + "\\LICENSE-VALVE.txt")
     copy_file(get_project_dir() + "\\third-party\\easylogging++\\LICENSE", get_deploy_dir() + "\\LICENSE-MIT.txt")
 
-    #res
-    copy_folder(get_project_dir() + "\\src\\res", get_deploy_dir() + "\\res")
-
     #package files
     copy_folder(get_project_dir() + "\\src\\package_files", get_deploy_dir())