api.thread_churn test failing on Windows due to reattach problems

My new test api.thread_churn for #4334 (closed) is failing on Windows due to some re-attach issues:

• .data is protected causing a crash on init
• failing to take over threads: 80 such messages on the re-attach:

<Detaching from process, entering final cleanup>
<Starting application D:\derek\dr\git\build_x64_dbg_tests\suite\tests\bin\api.thread_churn.exe (7644)>
<Running on newer-than-this-build "Microsoft Windows 10-1909 x64">
<Early threads found>
<Initial options = -no_dynamic_options -loglevel 2 -code_api -probe_api -msgbox_mask 0 -dumpcore_mask 125 -stderr_mask 15 -stack_size 56K -max_elide_jmp 0 -max_elide_call 0 -no_inline_ignored_syscalls -staged -native_exec_default_list '' -no_native_exec_managed_code -no_indcall2direct >
<CURIOSITY : (0) && "failed to take over a thread!" in file D:\derek\dr\git\src\core\win32\os.c line 2715
version 8.0.18444, custom build
-no_dynamic_options -loglevel 2 -code_api -probe_api -msgbox_mask 0 -dumpcore_mask 125 -stderr_mask 15 -stack_size 56K -max_elide_jmp 0 -max_elide_call 0 -no_inline_ignored_syscalls -staged -native_exec_default_list '' -no_native_exec_managed_code -no_indcall2direct >
<CURIOSITY : (0) && "failed to take over a thread!" in file D:\derek\dr\git\src\core\win32\os.c line 2715
version 8.0.18444, custom build
-no_dynamic_options -loglevel 2 -code_api -probe_api -msgbox_mask 0 -dumpcore_mask 125 -stderr_mask 15 -stack_size 56K -max_elide_jmp 0 -max_elide_call 0 -no_inline_ignored_syscalls -staged -native_exec_default_list '' -no_native_exec_managed_code -no_indcall2direct >
<...>

I tried to use logging to diagnose but hit another:

• log file not being opened Xref #2661 (closed) on ops appending: but here the option is not processed at all, leaving d_r_stats->loglevel 0.

It's not clear what's going on. The test makes 10 threads in the first burst. Is some state left over? Fixing logging would make it much easier to diagnose. For now I'm disabling the test on Windows.