Add ResolvePath tests (#276)

Add required computestorage APIs to allow for running tests of
`ResolvePath`.

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

internal/computestorage/zsyscall_windows.go

@@ -0,0 +1,77 @@
+//go:build windows
+
+// Code generated by 'go generate' using "github.com/Microsoft/go-winio/tools/mkwinsyscall"; DO NOT EDIT.
+
+package computestorage
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+var _ unsafe.Pointer
+
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoERROR_IO_PENDING = 997
+)
+
+var (
+	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+	errERROR_EINVAL     error = syscall.EINVAL
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return errERROR_EINVAL
+	case errnoERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	}
+	// TODO: add more here, after collecting data on the common
+	// error values see on Windows. (perhaps when running
+	// all.bat?)
+	return e
+}
+
+var (
+	modcomputestorage = windows.NewLazySystemDLL("computestorage.dll")
+
+	procHcsFormatWritableLayerVhd = modcomputestorage.NewProc("HcsFormatWritableLayerVhd")
+	procHcsGetLayerVhdMountPath   = modcomputestorage.NewProc("HcsGetLayerVhdMountPath")
+)
+
+func hcsFormatWritableLayerVhd(handle windows.Handle) (hr error) {
+	hr = procHcsFormatWritableLayerVhd.Find()
+	if hr != nil {
+		return
+	}
+	r0, _, _ := syscall.Syscall(procHcsFormatWritableLayerVhd.Addr(), 1, uintptr(handle), 0, 0)
+	if int32(r0) < 0 {
+		if r0&0x1fff0000 == 0x00070000 {
+			r0 &= 0xffff
+		}
+		hr = syscall.Errno(r0)
+	}
+	return
+}
+
+func hcsGetLayerVhdMountPath(vhdHandle windows.Handle, mountPath **uint16) (hr error) {
+	hr = procHcsGetLayerVhdMountPath.Find()
+	if hr != nil {
+		return
+	}
+	r0, _, _ := syscall.Syscall(procHcsGetLayerVhdMountPath.Addr(), 2, uintptr(vhdHandle), uintptr(unsafe.Pointer(mountPath)), 0)
+	if int32(r0) < 0 {
+		if r0&0x1fff0000 == 0x00070000 {
+			r0 &= 0xffff
+		}
+		hr = syscall.Errno(r0)
+	}
+	return
+}