Deny warnings in CI

Since we recently got rid of our last build/test/doc warnings, we now
deny warnings via `-D warnings` in CI, enforcing no new ones are
introduced.

Author: tnull

ci/ci-tests.sh

@@ -64,6 +64,7 @@ PIN_RELEASE_DEPS # pin the release dependencies in our main workspace
 [ "$RUSTC_MINOR_VERSION" -lt 65 ] && cargo update -p backtrace --precise "0.3.68" --verbose
 
 export RUST_BACKTRACE=1
+export RUSTFLAGS="-D warnings"
 
 echo -e "\n\nBuilding and testing all workspace crates..."
 cargo test --verbose --color always
@@ -92,14 +93,14 @@ if [[ "$HOST_PLATFORM" != *windows* ]]; then
 
 	DOWNLOAD_ELECTRS_AND_BITCOIND
 
-	RUSTFLAGS="--cfg no_download" cargo test --verbose --color always --features esplora-blocking
-	RUSTFLAGS="--cfg no_download" cargo check --verbose --color always --features esplora-blocking
-	RUSTFLAGS="--cfg no_download" cargo test --verbose --color always --features esplora-async
-	RUSTFLAGS="--cfg no_download" cargo check --verbose --color always --features esplora-async
-	RUSTFLAGS="--cfg no_download" cargo test --verbose --color always --features esplora-async-https
-	RUSTFLAGS="--cfg no_download" cargo check --verbose --color always --features esplora-async-https
-	RUSTFLAGS="--cfg no_download" cargo test --verbose --color always --features electrum
-	RUSTFLAGS="--cfg no_download" cargo check --verbose --color always --features electrum
+	RUSTFLAGS="$RUSTFLAGS --cfg no_download" cargo test --verbose --color always --features esplora-blocking
+	RUSTFLAGS="$RUSTFLAGS --cfg no_download" cargo check --verbose --color always --features esplora-blocking
+	RUSTFLAGS="$RUSTFLAGS --cfg no_download" cargo test --verbose --color always --features esplora-async
+	RUSTFLAGS="$RUSTFLAGS --cfg no_download" cargo check --verbose --color always --features esplora-async
+	RUSTFLAGS="$RUSTFLAGS --cfg no_download" cargo test --verbose --color always --features esplora-async-https
+	RUSTFLAGS="$RUSTFLAGS --cfg no_download" cargo check --verbose --color always --features esplora-async-https
+	RUSTFLAGS="$RUSTFLAGS --cfg no_download" cargo test --verbose --color always --features electrum
+	RUSTFLAGS="$RUSTFLAGS --cfg no_download" cargo check --verbose --color always --features electrum
 
 	popd
 fi
@@ -136,9 +137,9 @@ done
 
 for DIR in lightning lightning-invoice lightning-rapid-gossip-sync; do
 	# check if there is a conflict between no-std and the c_bindings cfg
-	RUSTFLAGS="--cfg=c_bindings" cargo test -p $DIR --verbose --color always --no-default-features --features=no-std
+	RUSTFLAGS="$RUSTFLAGS --cfg=c_bindings" cargo test -p $DIR --verbose --color always --no-default-features --features=no-std
 done
-RUSTFLAGS="--cfg=c_bindings" cargo test --verbose --color always
+RUSTFLAGS="$RUSTFLAGS --cfg=c_bindings" cargo test --verbose --color always
 
 # Note that outbound_commitment_test only runs in this mode because of hardcoded signature values
 pushd lightning