[build] Add configs for compile-only fuchsia trybot

TBR=tmrts@chromium.org

No-Try: true
Bug: chromium:1021522
Change-Id: I1f5f9bb4f9feb6eae34e62667421a8956c4d007e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1906382
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64874}

infra/mb/mb_config.pyl

@@ -189,6 +189,7 @@
       'v8_android_arm_compile_rel': 'release_android_arm',
       'v8_android_arm64_compile_dbg': 'debug_android_arm64',
       'v8_android_arm64_n5x_rel_ng': 'release_android_arm64',
+      'v8_fuchsia_compile_rel': 'release_x64_fuchsia_trybot',
       'v8_fuchsia_rel_ng': 'release_x64_fuchsia_trybot',
       'v8_ios_simulator': 'release_x64_ios_simulator',
       'v8_linux_rel_ng': 'release_x86_gcmole_trybot',