A number of Clang ToT bots are broken due to some ASAN reports like below:
https://build.chromium.org/p/chromium.fyi/builders/CrWinAsanCov/builds/2652/steps/compile/logs/stdio

319/27494] ACTION Generating yasm tokens for lc3b
FAILED: obj/third_party/yasm/yasm.gen/third_party/yasm/lc3bid.c 
C:\b\depot_tools\python276_bin\python.exe gyp-win-tool action-wrapper environment.x86 yasm_target_generate_lc3b_token_2995c673986e86381842b3a605763f4d..rsp ..\..\third_party\yasm
==3852==ERROR: AddressSanitizer failed to allocate 0x20000000 (536870912) bytes of CovInit (error code: 1455)
==3852==Dumping process modules:
	0x07730000-0x7772c000 C:\Windows\syswow64\msvcrt.dll
	0x5bbd0000-0x6bbd3000 C:\Windows\system32\api-ms-win-core-synch-l1-2-0.DLL
	0x65500000-0x7550c000 C:\Windows\syswow64\CRYPTBASE.dll
	0x74b40000-0x77679000 C:\Windows\SysWOW64\sechost.dll
	0xf7aa0000-0x756e0000 C:\Windows\syswow64\RPCRT4.dll
	0xf7c70000-0x75570000 C:\Windows\syswow64\SspiCli.dll
	0xf7db0000-0x75c20000 C:\Windows\syswow64\kernel32.dll
	0xf84c0000-0x75d57000 C:\Windows\syswow64\KERNELBASE.dll
	0xf9d20000-0x77d10000 C:\Windows\SysWOW64\ntdll.dll
	0xfea20000-0x76720000 C:\Windows\syswow64\ADVAPI32.dll
	0xffc80000-0x00589000 C:\b\c\b\CrWinAsanCov\src\out\Release\re2c.exe
==3852==AddressSanitizer CHECK failed: C:\b\c\b\CrWinAsanCov\src\third_party\llvm\projects\compiler-rt\lib\sanitizer_common\sanitizer_common.cc:120 "((0 && "unable to mmap")) != (0)" (0x0, 0x0)
    #0 0xa8527 in __sanitizer_update_counter_bitset_and_clear_counters+0x97 (C:\b\c\b\CrWinAsanCov\src\out\Release\re2c.exe+0x428527)
    #1 0xac9f3 in __sanitizer::CheckFailed+0x43 (C:\b\c\b\CrWinAsanCov\src\out\Release\re2c.exe+0x42c9f3)
    #2 0xb3efa in __sanitizer::ReportMmapFailureAndDie+0x5a (C:\b\c\b\CrWinAsanCov\src\out\Release\re2c.exe+0x433efa)
    #3 0xb5063 in __sanitizer::MmapNoReserveOrDie+0x33 (C:\b\c\b\CrWinAsanCov\src\out\Release\re2c.exe+0x435063)
    #4 0xa6e0a in __sanitizer::CoverageData::Enable+0x1a (C:\b\c\b\CrWinAsanCov\src\out\Release\re2c.exe+0x426e0a)
    #5 0xa833b in __sanitizer_cov_module_init+0x1b (C:\b\c\b\CrWinAsanCov\src\out\Release\re2c.exe+0x42833b)
    #6 0x81e32 in __local_stdio_scanf_options+0x62 (C:\b\c\b\CrWinAsanCov\src\out\Release\re2c.exe+0x401e32)
    #7 0xc1455 in __scrt_common_main_seh f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:221
    #8 0x75b23379 in BaseThreadInitThunk+0x11 (C:\Windows\syswow64\kernel32.dll+0x7dd73379)
    #9 0x77bc92b1 in RtlInitializeExceptionChain+0x62 (C:\Windows\SysWOW64\ntdll.dll+0x7dea92b1)
    #10 0x77bc9284 in RtlInitializeExceptionChain+0x35 (C:\Windows\SysWOW64\ntdll.dll+0x7dea9284)

The immediate issue is inability to allocate 512MB of memory, and the error code 1455 stands for:

ERROR_COMMITMENT_LIMIT
1455 (0x5AF)
The paging file is too small for this operation to complete.

So, we could either increase the page file on the bots, or stop requesting 512MB (sorry, I don't know specifics, why do we do that), or make sure there's such a contiguous chunk in the memory.

This is currently blocking the Clang roll.