ml64 [1] is set as the assembler for the Windows platform but is specific to the x64 platform. The armasm64 [2] assembler should be used for Windows AArch64.

The -Ta option is only valid for ml64 and should be removed from CompileFile.gmk (assembling for x64 works without it).

[1] https://learn.microsoft.com/en-us/cpp/assembler/masm/ml-and-ml64-command-line-reference?view=msvc-170
[2] https://learn.microsoft.com/en-us/cpp/assembler/arm/arm-assembler-command-line-reference?view=msvc-170