Add the toybox tests to bionic's presubmit.

I can't believe we didn't have this already.

Bug: http://b/236967833
Test: treehugger
Change-Id: Ic0fa7fd8e74860744d13d0c168b49240a86a8df2
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 08fac4f..18e8bbc 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -38,6 +38,9 @@
     },
     {
       "name": "memunreachable_unit_test"
+    },
+    {
+      "name": "toybox-tests"
     }
   ],
   "hwasan-presubmit": [
@@ -76,6 +79,9 @@
     },
     {
       "name": "memunreachable_unit_test"
+    },
+    {
+      "name": "toybox-tests"
     }
   ]
 }