Although support for building fiptool on a Windows host was present,
the binary was not built when the top level makefile was invoked.

This patch makes the necessary changes to the to support building of
fiptool on a Windows host PC from the main makefile.

Change-Id: I0c01ba237fa3010a027a1b324201131210cf4d7c
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>