When cross compiling the configure script will remove 'tools' from CFG_BUILD_PARTS leading to QtUiTools not being built at all. This appears to be true for cross compiling in general (be it embedded or X11).

From configure:
if [ -z "$CFG_BUILD_PARTS" ]; then
CFG_BUILD_PARTS="$QT_DEFAULT_BUILD_PARTS"

1. don't build tools by default when cross-compiling
   if [ "$PLATFORM" != "$XPLATFORM" ]; then
   CFG_BUILD_PARTS=`echo "$CFG_BUILD_PARTS" | sed "s, tools,,g"`
   fi
   fi