Use 8bit-counters when using libfuzzer

Reviewed-by: Rich Salz <rsalz@openssl.org>
GH: #2023

Configure

diff --git a/Configure b/Configure
index c005781..9d564ba 100755
--- a/Configure
+++ b/Configure
@@ -1111,7 +1111,7 @@
 }
 
 unless ($disabled{"fuzz-libfuzzer"}) {
-    $config{cflags} .= "-fsanitize-coverage=edge,indirect-calls ";
+    $config{cflags} .= "-fsanitize-coverage=edge,indirect-calls,8bit-counters ";
 }
 
 unless ($disabled{asan}) {