docker: Added fixed SOURCE_DATE_EPOCH flag for reproducible Fedora build

- Using environment variable `SOURCE_DATE_EPOCH` with fixed value will enforce a consistent timestamp for Fedora build.
. Similar to Ubuntu fix in commit 490fb0fc3b
- Locked cargo version
- Add `no-cache` to Fedora build

Changelog-Fixed: Core lightning builds for Fedora on all systems are deterministic.

contrib/docker/Dockerfile.builder.fedora

@@ -2,6 +2,8 @@ FROM fedora:40
 
 ENV UV_PYTHON=3.12
 ENV BITCOIN_VERSION=27.1
+ENV SOURCE_DATE_EPOCH=1672531200
+ENV RUSTFLAGS="-C link-arg=-Wl,--build-id=none"
 
 WORKDIR /tmp
 
@@ -20,7 +22,6 @@ RUN dnf update -y && \
 		jq \
 		xz \
 		zlib-devel \
-		cargo \
 		libsodium-devel \
 		which \
 		sed \
@@ -35,7 +36,7 @@ RUN dnf update -y && \
 	dnf clean all
 
 # Install Rust via rustup (for lockfile v4 support)
-RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain stable
+RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain 1.92.0
 ENV PATH="/root/.cargo/bin:${PATH}"
 
 # Install lowdown

tools/build-release.sh

@@ -177,7 +177,7 @@ for target in $TARGETS; do
         TAG=fedora
         DOCKERFILE=contrib/docker/Dockerfile.builder.fedora
         FEDORA_VERSION=$(grep -oP '^FROM fedora:\K[0-9]+' "$DOCKERFILE")
-        docker build -f $DOCKERFILE -t $TAG --load .
+        docker build --no-cache -f $DOCKERFILE -t $TAG --load .
         docker run --rm=true -v "$(pwd)":/src:ro -v "$RELEASEDIR":/release $TAG /src/tools/build-release.sh --inside-docker "$VERSION" "$platform" "$FEDORA_VERSION" "$ARCH" "$MAKEPAR"
         docker run --rm=true -w /build $TAG rm -rf /"$VERSION-$platform-$FEDORA_VERSION-$ARCH" /build
         echo "Fedora Image Built"