adding configuration for downloading linux_arm64 binary

[taustgen]

We are now publishing linux arm64 binaries, this adds them to the download rule.

Curl to show the binary name is endorctl_v1.6.744_linux_arm64

$curl -sS https://storage.googleapis.com/endorlabs/v1.6.744/manifest

endorctl_v1.6.744_linux_amd64 f37e1040dadf5d72288a621287ca039a0ddb62f828efbfa112c05b46a7163152
endorctl_v1.6.744_linux_arm64 50b6669651668145c6f92af1296949d89b251f19085bcddff7df9c44f0ee8231
endorctl_v1.6.744_macos_amd64 066a7b81c8a75f101b80c9f157dded87d8a07380a149c61811c0a5fa13bcb758
endorctl_v1.6.744_macos_arm64 a33c67a83c55723a04fea6b0cc9dc8dbd500c3cdce374fb087b873d46f511240
endorctl_v1.6.744_windows_amd64.exe eacc77c5485116796a3ddc2698fd82604f52e167d47b8df07c6b007b2f38d250
...

Curl to show the linux arm64 checksum name

$curl https://api.staging.endorlabs.com/meta/version/v1.6.744

{ ..., "ClientVersion":"v1.6.744","ClientChecksums": 
  { ... , "ARCH_TYPE_LINUX_ARM64":"50b6669651668145c6f92af1296949d89b251f19085bcddff7df9c44f0ee8231", ...}
}