Use ulimit -p rather than prlimit.

Neither is standard, but ulimit is toybox and therefore a bit more
regular and at least has help text.

Change-Id: Id7ba9adc9ca256b821d8060506010abef30dee28

envsetup.sh

@@ -1029,7 +1029,7 @@ function coredump_enable()
         return;
     fi;
     echo "Setting core limit for $PID to infinite...";
-    adb shell prlimit $PID 4 -1 -1
+    adb shell /system/bin/ulimit -p $PID -c unlimited
 }
 
 # core - send SIGV and pull the core for process