dashboard: don't set GOHOSTARCH=arm on arm64 Android devices

Building with GOHOSTARCH=arm on a GOHOSTARCH=arm64 android device
should work in theory, but results in an error about text relocations:

Building Go cmd/dist using /data/data/com.termux/files/home/go-android-arm64-bootstrap.
Building Go toolchain1 using /data/data/com.termux/files/home/go-android-arm64-bootstrap.
Building Go bootstrap cmd/go (go_bootstrap) using Go toolchain1.
warning: unable to find runtime/cgo.a
Building Go toolchain2 using go_bootstrap and Go toolchain1.
CANNOT LINK EXECUTABLE "/data/data/com.termux/files/usr/tmp/workdir-host-android-arm64-corellium-android/go/pkg/tool/android_arm/go_bootstrap": /data/data/com.termux/files/usr/tmp/workdir-host-android-arm64-corellium-android/go/pkg/tool/android_arm/go_bootstrap: has text relocations
go tool dist: FAILED: /data/data/com.termux/files/usr/tmp/workdir-host-android-arm64-corellium-android/go/pkg/tool/android_arm/go_bootstrap install -gcflags=all= -ldflags=all= -i cmd/asm cmd/cgo cmd/compile cmd/link: signal: aborted

I tried switching linker to gold, lld to no avail. Drop GOHOSTARCH
as a workaround.

Updates golang/go#31722

Change-Id: Id00564406582122f254c08b357668d7d0a9bae43
Reviewed-on: https://go-review.googlesource.com/c/build/+/175078
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: eliasnaur

dashboard/builders.go

@@ -1970,7 +1970,6 @@ func init() {
 		},
 		env: []string{
 			"CGO_ENABLED=1",
-			"GOHOSTARCH=arm",
 			"GOARCH=arm",
 		},
 	})