dashboard: set MallocNanoZone on ARM64 too

Accidentally removed in the fix for an accidental removal because I am
in too much of a hurry today.

Change-Id: I67a5518f36b051c2e99c0d3cabed3d61ce3401e9
Reviewed-on: https://go-review.googlesource.com/c/build/+/366234
Trust: Heschi Kreinick <heschi@google.com>
Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Alexander Rakoczy <alex@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/dashboard/builders.go b/dashboard/builders.go
index 98ac579..ad4dda4 100644
--- a/dashboard/builders.go
+++ b/dashboard/builders.go
@@ -542,6 +542,7 @@
 		Notes:     "macOS Big Sur (12.0) ARM64 (M1). Mac mini",
 		env: []string{
 			"GOROOT_BOOTSTRAP=/Users/gopher/goboot",
+			"MallocNanoZone=0", // golang.org/issue/49138
 		},
 		SSHUsername: "gopher",
 	},