Test `plugin5` failing on Windows with LLVM-10

[jamesmth]

When running:

opt --load-pass-plugin=plugin5.dll --passes="mpass,function(fpass)" tests/test.ll -disable-output

Exception 0x80000003 is raised, and the program fails with status code C0000374.

Call stack:

RtlIsZeroMemory (@RtlIsZeroMemory:62)
RtlpNtSetValueKey (@RtlpNtSetValueKey:355)
RtlpNtSetValueKey (@RtlpNtSetValueKey:567)
RtlpNtSetValueKey (@RtlpNtSetValueKey:7391)
RtlGetCurrentServiceSessionId (@RtlGetCurrentServiceSessionId:1274)
RtlFreeHeap (@RtlFreeHeap:24)
_free_base (@_free_base:10)
bool __cdecl llvm::runPassPipeline(class llvm::StringRef,class llvm::Module &,class llvm::TargetMachine *,class llvm::ToolOutputFile *,class llvm::ToolOutputFile *,class llvm::ToolOutputFile *,class llvm::StringRef,enum llvm::opt_tool::OutputKind,enum llvm::opt_tool::VerifierKind,bool,bool,bool,bool,bool) (d:\llvm-10.0.0.src\tools\opt\NewPMDriver.cpp:370)
main (d:\llvm-10.0.0.src\tools\opt\opt.cpp:707)
static int __scrt_common_main_seh() (@class llvm::ModulePass * llvm::createAMDGPUFixFunctionBitcastsPass(void):573419)
BaseThreadInitThunk (@BaseThreadInitThunk:9)
RtlUserThreadStart (@RtlUserThreadStart:12)