CI: Provide release flags, exclude -march=native

Author: ubaidsk

.github/workflows/CI.yml

@@ -335,6 +335,7 @@ jobs:
             export CXXFLAGS="-Werror"
             cmake . -GNinja \
               -DCMAKE_BUILD_TYPE=Release \
+              -DCMAKE_CXX_FLAGS_RELEASE="-Wall -Wextra -O3 -funroll-loops -DNDEBUG" \
               -DWITH_LLVM=yes \
               -DLFORTRAN_BUILD_ALL=yes \
               -DWITH_STACKTRACE=no \