package/s390-tools: also set HAVE_LIBCURL

Set HAVE_LIBCURL when libcurl is available to enable genprotimg and
libekmfweb:
https://github.com/ibm-s390-tools/s390-tools/blob/master/README.md

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Reviewed-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/s390-tools/s390-tools.mk

@@ -18,9 +18,13 @@ S390_TOOLS_MAKE_OPTS = \
 
 ifeq ($(BR2_PACKAGE_LIBCURL),y)
 S390_TOOLS_DEPENDENCIES += libcurl
-S390_TOOLS_MAKE_OPTS += HAVE_CURL=1
+S390_TOOLS_MAKE_OPTS += \
+	HAVE_CURL=1 \
+	HAVE_LIBCURL=1
 else
-S390_TOOLS_MAKE_OPTS += HAVE_CURL=0
+S390_TOOLS_MAKE_OPTS += \
+	HAVE_CURL=0 \
+	HAVE_LIBCURL=0
 endif
 
 ifeq ($(BR2_PACKAGE_JSON_C),y)