sngrep: gnutls support also needs libgcrypt

The gnutls support in sngrep not only needs gnutls, but also
libgcrypt. So only enable gnutls support when both packages are
available.

Fixes:

  http://autobuild.buildroot.net/results/18fbb5748a6ad66ac6ec8141c3296d2b13fa40ac/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/sngrep/sngrep.mk

@@ -18,7 +18,8 @@ SNGREP_CONF_OPTS += --disable-unicode
 ifeq ($(BR2_PACKAGE_OPENSSL),y)
 SNGREP_DEPENDENCIES += openssl
 SNGREP_CONF_OPTS += --with-openssl --without-gnutls
-else ifeq ($(BR2_PACKAGE_GNUTLS),y)
+# gnutls support also requires libgcrypt
+else ifeq ($(BR2_PACKAGE_GNUTLS)$(BR2_PACKAGE_LIBGCRYPT),yy)
 SNGREP_DEPENDENCIES += gnutls
 SNGREP_CONF_OPTS += --with-gnutls --without-openssl
 else