runtime: [tests] System.Text.Json.Tests segfault, for `Libraries Test Run checked coreclr Linux_musl x64 Debug`

Segfault seen in a test run: https://dev.azure.com/dnceng/public/_build/results?buildId=922206&view=ms.vss-test-web.build-test-results-tab&runId=29288458&paneView=debug&resultId=173384 on https://github.com/dotnet/runtime/pull/46048 .

+ ./RunTests.sh --runtime-path /root/helix/work/correlation
----- start Tue Dec 15 21:24:03 UTC 2020 =============== To repro directly: =====================================================
pushd .
/root/helix/work/correlation/dotnet exec --runtimeconfig System.Text.Json.Tests.runtimeconfig.json --depsfile System.Text.Json.Tests.deps.json xunit.console.dll System.Text.Json.Tests.dll -xml testResults.xml -nologo -nocolor -notrait category=IgnoreForCI -notrait category=OuterLoop -notrait category=failing 
popd
===========================================================================================================
/root/helix/work/workitem /root/helix/work/workitem
  Discovering: System.Text.Json.Tests (method display = ClassAndMethod, method display options = None)
  Discovered:  System.Text.Json.Tests (found 2250 of 2294 test cases)
  Starting:    System.Text.Json.Tests (parallel test collections = on, max threads = 2)
./RunTests.sh: line 161:    22 Segmentation fault      (core dumped) "$RUNTIME_PATH/dotnet" exec --runtimeconfig System.Text.Json.Tests.runtimeconfig.json --depsfile System.Text.Json.Tests.deps.json xunit.console.dll System.Text.Json.Tests.dll -xml testResults.xml -nologo -nocolor -notrait category=IgnoreForCI -notrait category=OuterLoop -notrait category=failing $RSP_FILE
/root/helix/work/workitem
----- end Tue Dec 15 21:24:32 UTC 2020 ----- exit code 139 ----------------------------------------------------------
exit code 139 means SIGSEGV Illegal memory access. Deref invalid pointer, overrunning buffer, stack overflow etc. Core dumped.