Use a different temp basedir for pytest to prevent long paths

azure-pipelines.yml

     steps:
       - script: |
           echo Loading VS environment
-          call "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Enterprise\\Common7\\Tools\\vsdevcmd" -arch=x64 || exit 1
+          call "C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\Common7\Tools\vsdevcmd" -arch=x64 || exit 1
           echo Executing Build and Tests
-          python -m pip install pytest pytest-xdist
-          python -u tools/ci.py -B download --cxx cl.exe -T tools\\msvc.dds -T2 tools\\msvc.p2.dds || exit 1
+          reg add HKLM\SYSTEM\CurrentControlSet\Control\FileSystem /v LongPathsEnabled /t REG_DWORD /d 1 /f || exit 1
+          python -m pip install pytest pytest-xdist || exit 1
+          python -u tools/ci.py -B download --cxx cl.exe -T tools\msvc.dds -T2 tools\msvc.p2.dds || exit 1
         displayName: Full CI
       - publish: _build/dds.exe
         artifact: DDS Executable - Windows VS2019

tools/ci.py

     self_deps_build(paths.CUR_BUILT_DDS, opts.toolchain_2,
                     paths.SELF_TEST_REPO_DIR,
                     paths.PROJECT_ROOT / 'remote.dds')
-    self_build(paths.CUR_BUILT_DDS, toolchain=opts.toolchain, lmi_path=paths.BUILD_DIR / 'INDEX.lmi')
-
-    return pytest.main(['-v', '--durations=10', '-n4'])
+    self_build(
+        paths.CUR_BUILT_DDS,
+        toolchain=opts.toolchain,
+        lmi_path=paths.BUILD_DIR / 'INDEX.lmi')
+
+    return pytest.main([
+        '-v',
+        '--durations=10',
+        f'--basetemp={paths.BUILD_DIR / "_tmp"}',
+        '-n4',
+    ])
 
 
 if __name__ == "__main__":