scripts/windows-build-deps.ps1 discovers the ARM64-capable Visual Studio
(vswhere -requires Microsoft.VisualStudio.Component.VC.Tools.ARM64) and
initializes VsDevCmd against it, then builds OpenSSL through vcpkg. But
vcpkg resolves Visual Studio on its own and takes the newest instance. On a
host with a second BuildTools install that lacks the native arm64 toolset,
the arm64-windows triplet fails:
error: in triplet arm64-windows: Unable to find a valid toolchain for
requested target architecture arm64.
The selected Visual Studio instance is at: ...\Microsoft Visual Studio\18\BuildTools
The available toolchain combinations are: x86, amd64, x86_amd64,
amd64_x86, arm64_x86, arm64_amd64
...in the same run that logs "-> ARM64 C++ build tools found: ...\2022\BuildTools".
The install fails, `hermes update` exits 1, the retry fails identically, and
the desktop relaunches on the previous build ("running with the previous
dependencies — run `hermes update` to finish it"), so it never updates.
Export the discovered instance as VCPKG_VISUAL_STUDIO_PATH, the documented
lever vcpkg's own error points at, without clobbering a caller's explicit pin
(same respect-if-set shape as CARGO_HOME/RUSTUP_HOME above).
Extends the initializer fixture: the discovered instance must be pinned when
unset, and a caller pin must survive the call. Needs a Windows runner — the
suite is platforms("windows") and the initializer refuses non-Windows hosts.
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