package/zchunk: needs argp

Fix the following build failure raised since the addition of the package
in commit c618da772df32679fdd338b99f44133655c9113f:

../output-1/build/zchunk-1.1.16/meson.build:35:4: ERROR: C shared or static library 'argp' not found

Fixes:
 - http://autobuild.buildroot.org/results/f82d06e95ac497aa8215268a7a58e929a05b32e3

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/zchunk/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_ZCHUNK
 	bool "zchunk"
+	select BR2_PACKAGE_ARGP_STANDALONE if BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_MUSL
 	select BR2_PACKAGE_LIBCURL
 	help
 	  A file format designed for highly efficient deltas while

package/zchunk/zchunk.mk

@@ -9,7 +9,9 @@ ZCHUNK_SITE = $(call github,zchunk,zchunk,$(ZCHUNK_VERSION))
 ZCHUNK_LICENSE = BSD-2-Clause
 ZCHUNK_LICENSE_FILES = LICENSE
 ZCHUNK_INSTALL_STAGING = YES
-ZCHUNK_DEPENDENCIES = libcurl
+ZCHUNK_DEPENDENCIES = \
+	libcurl \
+	$(if $(BR2_PACKAGE_ARGP_STANDALONE),argp-standalone)
 
 ifeq ($(BR2_PACKAGE_OPENSSL),y)
 ZCHUNK_DEPENDENCIES += openssl