Calling SetScriptingDefineSymbolsForGroup in batchmode

As part of our build process we update the script defines by calling UnityEditor.PlayerSettings:SetScriptingDefineSymbolsForGroup. This works fine, but Unity emits an error log saying:

Reload Assembly called from managed code directly. This will cause a crash. You should never refresh assets in synchronous mode or enter playmode synchronously from script code.

While normally this doesn't cause a problem, we do occasionally have a crash during the build. Obviously I'd prefer to have a way to prevent spurious crashes and to that end how can I have a build process modify scripting defines without triggering that ominous crash log?

Native stacktrace:

  0   libmonobdwgc-2.0.dylib              0x00000001308aabff mono_handle_native_crash + 242
  1   libsystem_platform.dylib            0x00007fffb89a6b3a _sigtramp + 26
  2   ???                                 0x0000000000008720 0x0 + 34592
  3   libsystem_c.dylib                   0x00007fffb882b420 abort + 129
  4   libmonobdwgc-2.0.dylib              0x0000000130a53550 GC_noop6 + 0
  5   libmonobdwgc-2.0.dylib              0x0000000130a27afb mono_unity_liveness_calculation_begin + 26
  6   Unity                               0x0000000100cfa19c _Z26GarbageCollectSharedAssetsb + 1436
  7   Unity                               0x0000000100e1eb55 _ZN27UnloadUnusedAssetsOperation19IntegrateMainThreadEv + 21
  8   Unity                               0x0000000100e1c8f2 _ZN14PreloadManager26UpdatePreloadingSingleStepENS_21UpdatePreloadingFlagsEi + 530
  9   Unity                               0x0000000100e1d44c _ZN14PreloadManager35WaitForAllAsyncOperationsToCompleteEv + 172
  10  Unity                               0x000000010276ef61 _ZN14AssetInterface27ProcessAssetsImplementationERd15CancelBehaviourN13AssetDatabase18UpdateAssetOptionsE + 1729
  11  Unity                               0x000000010276b7ce _ZN14AssetInterface16StopAssetEditingE15CancelBehaviourN13AssetDatabase18UpdateAssetOptionsE + 494
  12  Unity                               0x0000000102769295 _ZN14AssetInterface7RefreshEN13AssetDatabase18UpdateAssetOptionsE + 12629
  13  Unity                               0x0000000102722138 _ZN13AssetDatabase7RefreshENS_18UpdateAssetOptionsE + 232
  14  Unity                               0x0000000101b2c3c5 _ZN11Application17InitializeProjectEv + 11029
  15  Unity                               0x000000010074a139 _Z14NoGraphicsMainv + 41
  16  Unity                               0x000000010074a4ca _Z10EditorMainiPPKc + 826
  17  Unity                               0x000000010074a959 main + 9
  18  libdyld.dylib                       0x00007fffb8797235 start + 1