guix: configure with -Werror=dev

Author: fanquake

contrib/guix/libexec/build.sh

@@ -242,6 +242,7 @@ mkdir -p "$DISTSRC"
     cmake -S . -B build \
           --toolchain "${BASEPREFIX}/${HOST}/toolchain.cmake" \
           -DWITH_CCACHE=OFF \
+          -Werror=dev \
           ${CONFIGFLAGS}
 
     # Build Bitcoin Core