zlib: use default Build/Configure rule

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
(cherry picked from commit 462ca4e059)

package/libs/zlib/Makefile

@@ -45,17 +45,15 @@ define Package/zlib-dev/description
  This package includes the development support files.
 endef
 
-define Build/Configure
-	(cd $(PKG_BUILD_DIR); \
-		$(TARGET_CONFIGURE_OPTS) \
-		LDSHARED="$(TARGET_CC) -shared -Wl,-soname,libz.so.1" \
-		CFLAGS="$(TARGET_CFLAGS) $(FPIC)" \
-		./configure \
-			--prefix=/usr \
-			--shared \
-			--uname=Linux \
-	);
-endef
+CONFIGURE_VARS := \
+	$(TARGET_CONFIGURE_OPTS) \
+	LDSHARED="$(TARGET_CC) -shared -Wl,-soname,libz.so.1" \
+	CFLAGS="$(TARGET_CFLAGS) $(FPIC)" \
+
+CONFIGURE_ARGS := \
+	--prefix=/usr \
+	--shared \
+	--uname=Linux \
 
 define Build/Compile
 	+$(MAKE) $(PKG_JOBS) -C $(PKG_BUILD_DIR) \