Disable cross compile checks for libgcrypt usability
tests. They are not required.

--- configure	2015-10-18 14:02:02.423216637 +0200
+++ configure	2015-10-18 14:04:45.198228372 +0200
@@ -22294,7 +22294,7 @@
 
 		 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for libgcrypt usability" >&5
 $as_echo_n "checking for libgcrypt usability... " >&6; }
-                 if test "$cross_compiling" = yes; then :
+                 if test "$cross_compiling" = xxx; then :
   { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "cannot run test program while cross compiling
@@ -22334,7 +22334,7 @@
 
 				  { $as_echo "$as_me:${as_lineno-$LINENO}: result: ok" >&5
 $as_echo "ok" >&6; }
-                                  if test "$cross_compiling" = yes; then :
+                                  if test "$cross_compiling" = xxx; then :
   { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
 $as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
 as_fn_error $? "cannot run test program while cross compiling
