Add Windows Driver Kit (WDK) support for building KMDF/UMDF drivers

download --with-wdk fetches the WDK headers/libs/host-tools NuGet
packages (nuget.org has no vsman-manifest entry for this content) and
lays them out where the DriverKit.BuildTools PlatformToolset expects
them. msbuildEnv wires WDKContentRoot/WDKBuildFolder through
DisableRegistryUse the same way the SDK/toolset paths already are.

Two WDK-package fixups were needed for a real driver to actually
build under Wine: the bundled build-task assembly is versioned for an
older VisualStudioVersion than ours, and the package ships no x86
host-tools directory at all (only x64/arm64), which StampInf hardcodes
a path to.

Also force TZ=UTC for msbuild invocations: StampInf stamps DriverVer
using the local wall-clock date while Inf2Cat validates it against
UTC "now", so any timezone east of UTC sees a "postdated DriverVer"
failure for most of the day.

Verified against a real KMDF sample driver (microsoft/Windows-driver-
samples' echo_2): compiles, links, INF stamps and passes Inf2Cat's
signability check with SignMode=off.

internal/download/select.go

@@ -43,7 +43,15 @@ type Options struct {
 	SkipRecommended bool
 	Language        string
 
-	WithWDKInstallers string
+	// WithWDK selects the PlatformToolset registration
+	// (Component.Microsoft.Windows.DriverKit.BuildTools) that lets MSBuild
+	// recognize WindowsKernelModeDriver10.0/WindowsUserModeDriver10.0
+	// PlatformToolsets. It's not part of the manifest-driven default
+	// selection - unlike everything else it depends on, it's opt-in via
+	// --with-wdk, since the actual driver headers/libs come from a separate
+	// NuGet package download handled outside ExpandSelection entirely (see
+	// wdk.go and cmd/msvc-go-wine's runDownload).
+	WithWDK bool
 }
 
 func addIfWanted(opts *Options, flag TriState, pkg string) {
@@ -242,7 +250,7 @@ func ResolveSelection(opts *Options, idx Index) error {
 	addIfWanted(opts, opts.WithDevCmd, "Microsoft.VisualStudio.VC.vcvars")
 	addIfWanted(opts, opts.WithDevCmd, "Microsoft.VisualStudio.PackageGroup.VsDevCmd")
 
-	if opts.WithWDKInstallers != "" {
+	if opts.WithWDK {
 		opts.Package = append(opts.Package, "Component.Microsoft.Windows.DriverKit.BuildTools")
 	}