[build] Add new mac trybots

NOTRY=true
TBR=sergiyb@chromium.org

Bug: chromium:822593
Change-Id: I65427ed95da8d71ed690581aae3549e77003d264
Reviewed-on: https://chromium-review.googlesource.com/966102Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51976}

infra/mb/mb_config.pyl

@@ -231,7 +231,9 @@
       'v8_mac_dbg': 'debug_x86_trybot',
       'v8_mac_gc_stress_dbg': 'debug_x86_trybot',
       'v8_mac64_rel': 'release_x64_trybot',
+      'v8_mac64_rel_ng': 'release_x64_trybot',
       'v8_mac64_dbg': 'debug_x64',
+      'v8_mac64_dbg_ng': 'debug_x64',
       'v8_mac64_asan_rel': 'release_x64_asan_no_lsan',
       'v8_linux_arm_rel_ng': 'release_simulate_arm_trybot',
       'v8_linux_arm_dbg': 'debug_simulate_arm',