[openssl] Interrupt the build process when files conflict

[JackBoosY]

vcpkg/ports/openssl-windows/portfile.cmake

Lines 3 to 7 in 0a16cad

	if(EXISTS "${CURRENT_INSTALLED_DIR}/include/openssl/ssl.h")
	message(WARNING "Can't build openssl if libressl is installed. Please remove libressl, and try install openssl again if you need it. Build will continue but there might be problems since libressl is only a subset of openssl")
	set(VCPKG_POLICY_EMPTY_PACKAGE enabled)
	return()
	endif()

This will make other ports that rely on it unable to find the files generated by openssl when they are building, thus hiding this issue.

Fixes #12443.

[BillyONeal]

Thanks!