libxslt's crypto support uses libgcrypt, and at configure time, libgcrypt-config
is used to determine whether or not it's available.  Similar checks are used
for libxml2, but unlike for libxml2, no options are available to specify an
alternate prefix for libgcrypt.
For a cross-compilation configuration (configure --host=mingw32
--prefix=/usr/local/mingw32), this means that crypto cannot be enabled, nor will
it correctly be detected as unavailable - all because the build system's
libgcrypt-config will be called instead of that of the cross host.

Note: It would be even better if gnome libraries handled cross builds by
installing everything under $prefix/$host, with a $prefix/bin/$host-$program
symlink for every program/script it installs (the way binutils/gcc do it).
That would allow the use of AC_PATH_TOOL instead of AC_PATH_PROG to find the
correct config script.
In fact, even without that builtin support, simply using AC_CHECK/PATH_TOOL
instead of AC_CHECK/PATH_PROG in configure.in would at least allow people like
me to create those $host-$program links manually to fix build issues like this.