trap chmod errors in tar unpack on bsd - modes like 02755 fail

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@5656 3c298f89-4303-0410-b956-a3cf2f4a3e73

include/shell.sh

@@ -13,3 +13,18 @@ isset() {
 	eval "var=\"\${$1}\""
 	[ -n "$var" ]
 }
+
+trapret() {(
+	local retvals="$1"; shift
+	local cmd="$1"; shift
+	for retval in $(echo $retvals); do
+		local trap_$retval=1
+	done
+	"$cmd" "$@" || {
+		local retval="$?"
+		eval "trapped=\${trap_$retval}"
+		[ -n "$trapped" ] || {
+			return $retval
+		}
+	}
+)}