update-alternatives.bbclass: Disable for mingw32 targets
When building for mingw32 targets (e.g. nativesdk cross compiling for
windows), disable the dependency on update-alternatives as the Windows
platform does not support symlinks or package management.
This avoids the complex (partly non-buildable for mingw32) dependency
chain virtual/update-alternatives -> opkg-utils -> python -> ...
Signed-off-by: Nathan Rossi <nathan@nathanrossi.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
