doctor: skip checks for Linux/Mac-only pkgs

Skip checks for CIPD packages not available for Windows.

Change-Id: If5eb3513e21f4287a026609094ca1e9ddefba5ff
diff --git a/pw_doctor/py/pw_doctor/doctor.py b/pw_doctor/py/pw_doctor/doctor.py
index 12e8b04..34a103d 100755
--- a/pw_doctor/py/pw_doctor/doctor.py
+++ b/pw_doctor/py/pw_doctor/doctor.py
@@ -123,14 +123,19 @@
 
     commands_expected_from_cipd = [
         'arm-none-eabi-gcc',
-        'bazel',
-        'bloaty',
-        'clang++',
         'gn',
         'ninja',
         'protoc',
     ]
 
+    # TODO(mohrr) get these tools in CIPD for Windows.
+    if os.name == 'posix':
+        commands_expected_from_cipd += [
+            'bazel',
+            'bloaty',
+            'clang++',
+        ]
+
     for command in commands_expected_from_cipd:
         path = shutil.which(command)
         if path is None: