[Buildroot] [git commit branch/next] xmlstarlet: use $() to reference make variables instead of ${}

[Thomas Petazzoni]

commit: https://git.buildroot.net/buildroot/commit/?id=36305380db1312442623128689fe5067d9058381
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/next

Signed-off-by: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
---
 package/xmlstarlet/xmlstarlet.mk | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/package/xmlstarlet/xmlstarlet.mk b/package/xmlstarlet/xmlstarlet.mk
index 7039d77..98efd07 100644
--- a/package/xmlstarlet/xmlstarlet.mk
+++ b/package/xmlstarlet/xmlstarlet.mk
@@ -15,9 +15,9 @@ XMLSTARLET_DEPENDENCIES += libxml2 libxslt \
 	$(if $(BR2_PACKAGE_LIBICONV),libiconv)
 
 XMLSTARLET_CONF_OPTS += \
-	--with-libxml-prefix=${STAGING_DIR}/usr \
-	--with-libxslt-prefix=${STAGING_DIR}/usr \
-	--with-libiconv-prefix=${STAGING_DIR}/usr
+	--with-libxml-prefix=$(STAGING_DIR)/usr \
+	--with-libxslt-prefix=$(STAGING_DIR)/usr \
+	--with-libiconv-prefix=$(STAGING_DIR)/usr
 
 ifeq ($(BR2_STATIC_LIBS),y)
 XMLSTARLET_CONF_OPTS += --enable-static-libs