opkg: gracefully handle missing $PATH, fix build warnings

Update to latest Git in order to import the following fixes:

cfe46c7 opkg_active_list_test: mark functions static, swap strcmp() with memcmp()
0b60d6a libopkg_test: mark functions static, remove unused opkg_test()
28b5e15 pkg_parse: fix bad message level for opkg_msg() call
d9e5814 pkg_parse: remove unused variable in pkg_parse_line()
1654bcc pkg_parse: remove const requirement from pkg_parse_line()
53e199e pkg_hash: remove unused variable in pkg_hash_load_feeds()
da8d599 pkg_depends: add missing parse_replacelist() prototype
f0c0a80 opkg_utils: add missing header
e450488 libopkg: remove unused progress parameters from opkg_download()
f4a55d1 libopkg: remove unused progress callback
7cbc466 libopkg: remove unused variable from opkg_install_package()
6fbf8a9 libbb: remove unused variables
7975c73 libbb: change gzip_read() buffer argument to void *
6e28563 libbb: fix gzip_thread() warnings
1ff2475 libopkg/opkg_cmd.c: more robust PATH handling
5dc3e33 libopkg: specify "/bin/sh" instead of "sh"

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

package/system/opkg/Makefile

@@ -16,9 +16,9 @@ PKG_FLAGS:=essential
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://git.lede-project.org/project/opkg-lede.git
-PKG_SOURCE_DATE:=2017-03-01
-PKG_SOURCE_VERSION:=19070b6c1a9718bf7ceaa61c48f328cabf1d5ca7
-PKG_MIRROR_HASH:=7fa506c752db01fff47522141e8349603485368ae955315fc41754aec9ecee13
+PKG_SOURCE_DATE:=2017-03-15
+PKG_SOURCE_VERSION:=cfe46c7d5787df0bd643d44e8f985107b562300e
+PKG_MIRROR_HASH:=abc0c125c856318a457add3d2c5ec668464ed962ccfc688ea1cbd5047b435f23
 
 PKG_LICENSE:=GPL-2.0
 PKG_LICENSE_FILES:=COPYING
@@ -26,7 +26,7 @@ PKG_LICENSE_FILES:=COPYING
 PKG_MAINTAINER:=Jo-Philipp Wich <jo@mein.io>
 
 PKG_FLAGS := nonshared
-PKG_CONFIG_DEPENDS := CONFIG_SIGNED_PACKAGES
+PKG_CONFIG_DEPENDS := CONFIG_SIGNED_PACKAGES CONFIG_TARGET_INIT_PATH
 
 PKG_BUILD_PARALLEL:=1
 HOST_BUILD_PARALLEL:=1
@@ -69,6 +69,7 @@ EXTRA_CFLAGS += $(TARGET_CPPFLAGS)
 CMAKE_OPTIONS += \
 	-DBUILD_TESTS=OFF \
 	-DHOST_CPU=$(PKGARCH) \
+	-DPATH_SPEC="$(TARGET_INIT_PATH)" \
 	-DVERSION="$(PKG_SOURCE_VERSION) ($(PKG_SOURCE_DATE))"
 
 CMAKE_HOST_OPTIONS += \