cmake: Enable COPY_DEPENDENCIES by default on Windows

When setting up a build for the first time on windows, makes it so you
no longer have to run cmake twice:  once to build, then once again with
the COPY_DEPENDENCIES box to ensure dependencies are copied.

Closes jp9000/obs-studio#768

cmake/Modules/CopyMSVCBins.cmake

@@ -8,7 +8,7 @@ if(COPIED_DEPENDENCIES)
 	return()
 endif()
 
-option(COPY_DEPENDENCIES "Automaticaly try copying all dependencies" OFF)
+option(COPY_DEPENDENCIES "Automaticaly try copying all dependencies" ON)
 if(NOT COPY_DEPENDENCIES)
 	return()
 endif()