[build] Prepare switching cfi bot to GN

Explicitly set argument for use_cfi_recover introduced in:
https://codereview.chromium.org/2920963002

This retains the behavior we had in GYP:
Print useful diagnostics, but crash to make the errors show up.

Also set use_cfi_cast=true. In gyp we've set this by default:
-fsanitize=cfi-derived-cast
-fsanitize=cfi-unrelated-cast

In GN it now lives behind the use_cfi_cast flag.

NOTRY=true
TBR=vogelheim@chromium.org

Bug: chromium:726584
Change-Id: If202bc42fff3d5ff398576a114af7a7c3fb3fd2b
Reviewed-on: https://chromium-review.googlesource.com/528175Reviewed-by: Daniel Vogelheim <vogelheim@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45848}

infra/mb/mb_config.pyl

@@ -524,7 +524,8 @@
     },
 
     'cfi': {
-      'gn_args': 'is_cfi=true use_cfi_diag=true',
+      'gn_args': ('is_cfi=true use_cfi_cast=true use_cfi_diag=true '
+                  'use_cfi_recover=false'),
       'gyp_defines': 'cfi_vptr=1 cfi_diag=1',
     },