Fix SPEC CPU win-arm64 build failure caused by invalid -march=armv8-a

[ericavella]

Problem

The QoS_VC_*_PERF-SPECCPU-*-win-arm64 goals report WORKLOAD METRICS: MISSING — VirtualClient runs for the full execution window but emits zero SPEC metrics.

Root cause: on Windows the SPEC CPU 2017 toolchain is always the x86_64 Cygwin GCC (there is no Arm64 Cygwin distribution). On win-arm64 it runs under x64 emulation and targets x86_64. The PERF-SPECCPU-*.json profiles derived the optimizing flags purely from CPU architecture:

-march={calculate("{Architecture}" == "x64" ? "native" : "armv8-a")}

On win-arm64 this yields -march=armv8-a, which the x86_64 Cygwin gcc/gfortran reject:

cc1:  error: bad value 'armv8-a' for '-march=' switch
f951: Error: bad value 'armv8-a' for '-march=' switch

Every benchmark's specmake build fails (exit 2), but runspeccpu.bat still returns exit 0, so SpecCpuExecutor emits no metrics and the failure surfaces as "metrics missing" rather than a build error.

Fix

On any Windows platform (Cygwin ⇒ x86_64) resolve -march to native. Only linux-arm64 continues to use armv8-a.

-march={calculate(("{Platform}".StartsWith("win") || "{Architecture}" == "x64") ? "native" : "armv8-a")}

Applied to all four profiles: PERF-SPECCPU-FPRATE/FPSPEED/INTRATE/INTSPEED.json.

Validation

• Reproduced the exact make.out compiler error on a real win-arm64 (Cobalt 100) VM using x86_64 Cygwin gcc/gfortran 14.4.0, and confirmed -march=native compiles cleanly (exit 0).
• Added a ProfileExpressionEvaluator regression test covering win-arm64 → native, win-x64 → native, linux-x64 → native, linux-arm64 → armv8-a.
• Existing SpecCpuProfileTests parameter-inlining tests pass for all four profiles.

Note

Separately, runspeccpu.bat / SpecCpuExecutor swallow the specmake build failure (exit 0), which is what turned this into a silent "metrics missing" instead of a hard failure. That robustness fix is out of scope here but worth a follow-up.

[azure-pipelines]

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