cross compile fix by (allanc at chickenandporn dot com)

Originally committed as revision 3384 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -799,8 +799,12 @@ EOF
 have_lrintf="no"
 if $cc $extralibs -o $TMPE $TMPC 2> /dev/null ; then
   have_lrintf="yes"
+  # allanc@chickenandporn.com: cannot execute cross-compiled
+  # code on the host.  Only execute if not cross-compiling.
+  if test -z "$cross_prefix" ; then
     $TMPE 2> /dev/null > /dev/null || have_lrintf="no"
   fi
+fi
 
 _restrict=
 for restrict_keyword in restrict __restrict__ __restrict; do