Prerequisites: For repro the following setup is needed:
- An Apple machine with discrete GPU having more than 4GB of VRAM and (possibly) with AMD GPU;
- The Editor trunk build downloaded through Katana or Unity QA-multi tool.

Steps to repro:

1. Open the attached project and 'ProgressiveLightmappingExample' scene on OSX;
2. In the Lighting window change the Lightmapper to Progressive GPU;
3. In the Lighting window press 'Generate Lighting' button.

Expected result:
Bake proceeds and finishes without errors.

Actual result:
After some time Editor becomes completely unresponsive and the machine either shows BSOD (kernel panic error) and reboots (very often) or Unity crashes (not often).
The following callstack is shown after the crash:
Obtained 18 stack frames.
Thread 0x70000245c000 may have been prematurely finalized
#0 0x007fff67ba52c6 in __pthread_kill
Thread 0x70000245c000 may have been prematurely finalized
#1 0x007fff67b0f6a6 in abort
Thread 0x70000245c000 may have been prematurely finalized
#2 0x007fff56bd4240 in gpumCreateComputeContext
Thread 0x70000245c000 may have been prematurely finalized
#3 0x0000014c761943 in gpusKillClientExt
Thread 0x70000245c000 may have been prematurely finalized
#4 0x007fff56bd4bbd in gpusQueueSubmitDataBuffers
Thread 0x70000245c000 may have been prematurely finalized
#5 0x0000014c7423fd in glrAMDCompSubmitPackets
Thread 0x70000245c000 may have been prematurely finalized
#6 0x0000014c7422e0 in glrAMDFlush
Thread 0x70000245c000 may have been prematurely finalized
#7 0x0000014c75d7c0 in glrATIExecuteKernel
Thread 0x70000245c000 may have been prematurely finalized
#8 0x0000014c760bdc in gldExecuteKernel
Thread 0x70000245c000 may have been prematurely finalized
#9 0x007fff4422f184 in clFlush
Thread 0x70000245c000 may have been prematurely finalized
#10 0x007fff4424707c in clSetEventCallback
Thread 0x70000245c000 may have been prematurely finalized
#11 0x007fff44248fd2 in clCreateCommandQueueWithPropertiesAPPLE
Thread 0x70000245c000 may have been prematurely finalized
#12 0x007fff67a1d63d in _dispatch_client_callout
Thread 0x70000245c000 may have been prematurely finalized
#13 0x007fff67a238e0 in _dispatch_lane_serial_drain
Thread 0x70000245c000 may have been prematurely finalized
#14 0x007fff67a24396 in _dispatch_lane_invoke
Thread 0x70000245c000 may have been prematurely finalized
#15 0x007fff67a2c6ed in _dispatch_workloop_worker_thread
Thread 0x70000245c000 may have been prematurely finalized
#16 0x007fff67c5d611 in _pthread_wqthread
Thread 0x70000245c000 may have been prematurely finalized
#17 0x007fff67c5d3fd in start_wqthread

See attached log files.
Regression introduced in Unity 2019.3.0a3

Notes:
- Reproducible in 2019.3.0a3, 2019.3.0a5;
- Not reproducible in 2019.3.0a2, 2019.2.0b5;
- Reproducible on OSX 10.14.5 on MacBookPro mid 2017 with AMD GPU (2 GB VRAM);
- Not reproducible on Windows 10 (NVIDIA GeForce GTX 1070);
- Could not test on Saihai build Editor, since of this blocking bug: https://fogbugz.unity3d.com/f/cases/1120397/;
- Happening only on GPU PLM; not reproducible on CPU PLM.