add back linux gpu jobs

Author: osalpekar

.circleci/config.yml

@@ -233,10 +233,12 @@ def indent(indentation, data_list):
 
 def unittest_workflows(indentation=6):
     jobs = []
-    for os_type in ["windows", "macos"]:
+    for os_type in ["linux", "windows", "macos"]:
         for device_type in ["cpu", "gpu"]:
             if os_type == "macos" and device_type == "gpu":
                 continue
+            if os_type == "linux" and device_type == "cpu":
+                continue
             for i, python_version in enumerate(PYTHON_VERSIONS):
                 job = {
                     "name": f"unittest_{os_type}_{device_type}_py{python_version}",