Failed vm-win-release-x64-try build with crashpad_handler.exe permission denied

[aam]

https://logs.chromium.org/logs/dart/buildbucket/cr-buildbucket/8727463111126319345/+/u/build_dart/stdout

[3319/3363] LINK ./crashpad_handler.exe
FAILED: crashpad_handler.exe crashpad_handler.lib crashpad_handler.exe.pdb 
C:/b/s/w/ir/cipd_bin_packages/cpython3/bin/python3.exe ../../build/toolchain/win/tool_wrapper.py link-wrapper environment.x64 False ../../buildtools/win-x64/clang/bin/lld-link.exe /nologo /OUT:./crashpad_handler.exe /PDB:./crashpad_handler.exe.pdb @./crashpad_handler.exe.rsp
lld-link: error: failed to write output './crashpad_handler.exe': permission denied

[aam]

happened again https://logs.chromium.org/logs/dart/buildbucket/cr-buildbucket/8727457511316612497/+/u/build_dart/stdout

[aam]

the earliest so far seems to be from 12/20 https://logs.chromium.org/logs/dart/buildbucket/cr-buildbucket/8728004320607827601/+/u/build_dart/stdout

[aam]

https://ci.chromium.org/ui/p/dart/builders/ci.sandbox/vm-win-release-x64/5869
and
https://ci.chromium.org/ui/p/dart/builders/ci.sandbox/vm-win-debug-x64/5425

[mraleph]

We probably need code in test.py to make sure that all stale crashpad_handler.exe processes are killed.

[aam]

I landed https://dart.googlesource.com/sdk/+/68849148fde1b07aa1ca18af92139a144b773413 that does that.