opkg_manager: use system-update script if available

opkg has several problems with complex system updates, especially when
having to update itself and with the package ordering during update
To avoid hard coding the workarounds into neutrino, just call a script
named "system-update" (if available) instead of "opkg upgrade".
This script can be tuned to the specific target and its problems.


Origin commit data
------------------
Branch: ni/coolstream
Commit: fd9387a43c
Author: Stefan Seyfried <seife@tuxbox-git.slipkontur.de>
Date: 2017-01-29 (Sun, 29 Jan 2017)



------------------
This commit was generated by Migit

src/gui/opkg_manager.cpp

@@ -11,7 +11,7 @@
 	Adaptions:
 	Copyright (C) 2013 martii
 	gitorious.org/neutrino-mp/martiis-neutrino-mp
-	Copyright (C) 2015-2016 Stefan Seyfried
+	Copyright (C) 2015-2017 Stefan Seyfried
 
 	License: GPL
 
@@ -71,6 +71,11 @@
 #define OPKG_BAD_PATTERN_LIST_FILE CONFIGDIR "/bad_package_pattern.list"
 #define OPKG_CONFIG_FILE "/etc/opkg/opkg.conf"
 
+/* script to call instead of "opkg upgrade"
+ * opkg fails to gracefully self-upgrade, and additionally has some ordering issues
+ */
+#define SYSTEM_UPDATE "system-update"
+
 using namespace std;
 
 enum
@@ -89,7 +94,7 @@ enum
 	OM_MAX
 };
 
-static const string pkg_types[OM_MAX] =
+static string pkg_types[OM_MAX] =
 {
 	OPKG_CL " list ",
 	OPKG_CL " list-installed ",
@@ -614,6 +619,11 @@ bool COPKGManager::hasOpkgSupport()
 		return false;
 	}
 
+	if (! find_executable(SYSTEM_UPDATE).empty()) {
+		dprintf(DEBUG_NORMAL, "[COPKGManager] [%s - %d] " SYSTEM_UPDATE " script found\n", __func__, __LINE__);
+		pkg_types[OM_UPGRADE] = SYSTEM_UPDATE;
+	}
+
 #if 0
 	/* If directory /var/lib/opkg resp. /opt/opkg
 	   does not exist, it is created by opkg itself */