Add support for building native win32 tools

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>
diff --git a/README b/README
index fcc4d7c..142dbcc 100644
--- a/README
+++ b/README
@@ -2716,6 +2716,16 @@
 	$ CROSS_COMPILE=ppc_4xx-
 	$ export CROSS_COMPILE
 
+Note: If you wish to generate Windows versions of the utilities in
+      the tools directory you can use the MinGW toolchain
+      (http://www.mingw.org).  Set your HOST tools to the MinGW
+      toolchain and execute 'make tools'.  For example:
+
+       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
+
+      Binaries such as tools/mkimage.exe will be created which can
+      be executed on computers running Windows.
+
 U-Boot is intended to be simple to build. After installing the
 sources you must configure U-Boot for one specific board type. This
 is done by typing: