validate json output of viz.cli in CI (#17232)

* validate viz.cli --json always prints valid JSON

* highest debug level

* jq empty we don't need a print

* gate that import

.github/workflows/test.yml

@@ -176,6 +176,7 @@ jobs:
       run: |
         DEV=NULL python3 -m unittest test.backend.test_multitensor.TestMultiTensor.test_data_parallel_resnet_train_step
         DEV=NULL VIZ=1 python3 -m pytest -n=auto test/null/test_viz.py
+        DEBUG=7 python -m tinygrad.viz.cli --json | jq empty
     # TODO: too slow
     # - name: Run SDXL on NULL backend
     #   run: DEV=NULL DEBUG=1 python3 examples/sdxl.py --seed 0 --noshow --timing --fakeweights

tinygrad/engine/realize.py

@@ -261,7 +261,7 @@ pm_exec = PatternMatcher([
   (UPat(Ops.CALL, src=(UPat(Ops.CUSTOM_FUNCTION, arg="validate", name="ast"),), name="call", allow_any_len=True), exec_validate),
 ])
 
-from tinygrad.runtime.support.hcq2 import hcq_compile, hcq_link # noqa: E402 # down here, hcq2 imports the helpers above
+if getenv("HCQ2"): from tinygrad.runtime.support.hcq2 import hcq_compile, hcq_link # noqa: E402 # down here, hcq2 imports the helpers above
 
 def compile_linear(linear:UOp, beam:int|None=None, validate=False, input_uops:list[UOp]|None=None, jit=False) -> UOp:
   if validate: linear = graph_rewrite(linear, pm_validate, name="validate", walk=True)