fuzz: use debug fuzzers
Debug builds generally have more assertions, so it's more likely an
issue can be found.
diff --git a/fuzz/Dockerfile b/fuzz/Dockerfile
index 63e7693..ecd2085 100644
--- a/fuzz/Dockerfile
+++ b/fuzz/Dockerfile
@@ -9,6 +9,6 @@
COPY ./cert.crt ./
COPY ./cert.key ./
-COPY ./target/x86_64-unknown-linux-gnu/release/packet_recv_client ./
-COPY ./target/x86_64-unknown-linux-gnu/release/packet_recv_server ./
-COPY ./target/x86_64-unknown-linux-gnu/release/qpack_decode ./
+COPY ./target/x86_64-unknown-linux-gnu/debug/packet_recv_client ./
+COPY ./target/x86_64-unknown-linux-gnu/debug/packet_recv_server ./
+COPY ./target/x86_64-unknown-linux-gnu/debug/qpack_decode ./
