boringssl: set -march=armv8-a+crypto on arm64

Modified from https://codereview.chromium.org/1475393002/ by Riku Voipio
<[email protected]>.

In the boringssl commit a91fd063cf87b905a4d3b06387727deb4a7016d0 [1]
.arch armv8-a+crypto has been disabled for clang.

So -march=armv8-a+crypto now needs to be set on command line to
build chromium/boringssl with clang. This commit fixes debian/arm64
chromium build.

[1] https://boringssl-review.googlesource.com/4411

BUG=none

Review URL: https://codereview.chromium.org/1574073003

Cr-Commit-Position: refs/heads/master@{#369247}
diff --git a/AUTHORS b/AUTHORS
index c2dc982..0d5e225 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -489,6 +489,7 @@
 Rene Bolldorf <[email protected]>
 Rene Ladan <[email protected]>
 Rijubrata Bhaumik <[email protected]>
+Riku Voipio <[email protected]>
 Rob Buis <[email protected]>
 Rob Wu <[email protected]>
 Robert Bear Travis <[email protected]>