cmark: fix UPDATE macro and exploit GH_CONF

src/cmark.mk

@@ -6,15 +6,9 @@ $(PKG)_DESCR    := CommonMark parsing and rendering library and program in C
 $(PKG)_IGNORE   :=
 $(PKG)_VERSION  := 0.28.3
 $(PKG)_CHECKSUM := acc98685d3c1b515ff787ac7c994188dadaf28a2d700c10c1221da4199bae1fc
-$(PKG)_SUBDIR   := $(PKG)-$($(PKG)_VERSION)
-$(PKG)_FILE     := $(PKG)-$($(PKG)_VERSION).tar.gz
-$(PKG)_URL      := https://github.com/commonmark/cmark/archive/$($(PKG)_VERSION).tar.gz
+$(PKG)_GH_CONF  := commonmark/cmark/releases
 $(PKG)_DEPS     := cc
 
-define $(PKG)_UPDATE
-    $(call MXE_GET_GITHUB_TAGS, commonmark/cmark)
-endef
-
 define $(PKG)_BUILD
     cd '$(BUILD_DIR)' && \
         '$(TARGET)-cmake' '$(SOURCE_DIR)' \