Regression in tool.drcacheoff.burst* tests on Github Actions

The following tests have recently started failing on the Github Actions workflow for x86-64:

	code_api|tool.drcacheoff.burst_static 
	code_api|tool.drcacheoff.burst_replace 
	code_api|tool.drcacheoff.burst_replaceall 
	code_api|tool.drcacheoff.burst_noreach 
	code_api|tool.drcacheoff.burst_maps 
	code_api|tool.drcacheoff.burst_traceopts 
	code_api|tool.drcacheoff.burst_threads 
	code_api|tool.drcacheoff.burst_malloc 
	code_api|tool.drcacheoff.burst_reattach 
	code_api|tool.drcacheoff.burst_threadL0filter 
	code_api|tool.drcacheoff.burst_client 

This is blocking some PRs, including #5569, #5568 and #5562.

Logs: https://github.com/DynamoRIO/dynamorio/runs/7430951767?check_suite_focus=true

2022-07-20T14:16:23.9265812Z 349:   <Application
2022-07-20T14:16:23.9266263Z 349:   /home/runner/work/dynamorio/dynamorio/build_debug-internal-64/clients/bin64/tool.drcacheoff.burst_threads
2022-07-20T14:16:23.9266655Z 349:   (24791).  Internal Error: DynamoRIO debug check failure:
2022-07-20T14:16:23.9266991Z 349:   /home/runner/work/dynamorio/dynamorio/core/unix/signal.c:5861
2022-07-20T14:16:23.9267422Z 349:   syscall_signal || safe_is_in_fcache(dcontext, pc, (byte *)sc->SC_XSP)