Use $BINDIR as the default helper binary directory on Windows

The default helper binary directory on Windows was hardcoded. However
the new user-scope installer deploys the binaries on a distinct
directory. As a consequence `podman machine start` fails because
gvproxy/winssh-proxy cannot be found.

This problem affects Hyper-V, not WSL.

To fix the problem we are using $BINDIR that is used by the function
FindHelperBinaries to look in the directory where podman is located.

Fixes containers/podman#27603

Signed-off-by: Mario Loriedo <[email protected]>

Author: l0rd

common/pkg/config/config_windows.go

@@ -31,5 +31,7 @@ func overrideContainersConfigPath() (string, error) {
 }
 
 var defaultHelperBinariesDir = []string{
-	"C:\\Program Files\\RedHat\\Podman",
+	// FindHelperBinaries(), as a convention, interprets $BINDIR as the
+	// directory where the current process binary (i.e. podman) is located.
+	"$BINDIR",
 }