At least on OS X 10.5 and older, getline does not exist.  So split out the
function from the mingw code so that we can pull it in for Darwin systems.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

mkimage does not build due to missing strtok_r() and getline() implementation

Signed-off-by: Remy Bohmer <linux@bohmer.net>

Add support for compiling the host tools in the tools directory using
the MinGW toolchain.  This produces executables which can be used on
standard Windows computers without requiring cygwin.

One must specify the MinGW compiler and strip utilities as if they
were the host toolchain in order to build win32 executables, eg:

make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>