Switch printenv to toybox.

Change-Id: I53362a14b3c3ed290844c840e9d5523e8c042d22
diff --git a/Android.mk b/Android.mk
index 2d22f5c..da6412b 100644
--- a/Android.mk
+++ b/Android.mk
@@ -183,7 +183,7 @@
 LOCAL_MODULE := toybox
 
 # dupes: cat chmod chown cmp cp date df dmesg du grep id ifconfig kill ls mkdir
-#        mknod mkswap mount mv nc netcat nohup notify(inotifyd) printenv readlink renice rm rmdir
+#        mknod mkswap mount mv nc netcat nohup notify(inotifyd) readlink renice rm rmdir
 #        swapoff swapon touch umount vmstat
 # obsolete?: cpio killall5 link unlink
 # non-Linux: count freeramdisk fstype nbd-client oneit vconfig
@@ -237,6 +237,7 @@
     patch \
     pidof \
     pmap \
+    printenv \
     pwd \
     readahead \
     realpath \