Don't build/test binaries with cargo test to workaround OOM issues

what I am seeing with the move to Linode VMs is essentially this:
rust-lang/cargo#9157
rust-lang/cargo#12912

B/c these new VMs have more CPU cores, 16 (new) vs 4(old),
compilation is faster however this causes cargo to be overzealous and
spawn too many linker processes which consume all of the available
memory (on a 64 GB VM) and causes an OOM error forcing the kernel to
kill the linker process and causing cargo to fail!

Another alternative, which works, is using `--jobs 8`, however that is
less optimal b/c it leaves unused CPU capacity and also affects the
number of parallel threads when executing the test suite!

WARNING: using `--release` is not an option because it breaks tests. The
polkadot-sdk code uses the macro defensive! which is designed to panic
when running in debug mode and multiple test scenarios rely on this
behavior via #[should_panic]!

WARNING: we still need the 64 GB memory!

.github/workflows/gluwa.yml

@@ -140,7 +140,7 @@ jobs:
         uses: gluwa/cargo@dev
         with:
           command: test
-          args: --features runtime-benchmarks
+          args: --features runtime-benchmarks --lib
 
   rm-gh-runner-cargo-check:
     runs-on: ubuntu-latest