This fixes error reported by clang: unused variable 'kKeyArgTag' [-Werror,-Wunused-const-variable]. Change-Id: I1d5c9937064bfadd810cbe1b73e0070cc2ead684 Signed-off-by: Piotr Sikora <piotr@cloudflare.com> Reviewed-on: https://boringssl-review.googlesource.com/2070 Reviewed-by: Adam Langley <agl@google.com>kris/onging/CECPQ3_patch15