[fuzzer] Check enum type at compile time

I think this originally was done due to int / unsigned
differences between Linux in Windows.  In hindsight, that
was short-sighted.

Bug: oss-fuzz:11281,oss-fuzz:11282,oss-fuzz:11283
Change-Id: I06e38cb663f84278f479eb7fee3118c1068eeaa8
Reviewed-on: https://skia-review.googlesource.com/c/169244
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
1 file changed