tests/functional/test_sparc64_tuxrun: Explicitly set the 'sun4u' machine

Use self.set_machine() to set the machine instead of relying on the
default machine of the binary. This way the test can be skipped in
case the machine has not been compiled into the QEMU binary.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20250521145112.142222-1-thuth@redhat.com>
diff --git a/tests/functional/test_sparc64_tuxrun.py b/tests/functional/test_sparc64_tuxrun.py
index 3be08d6..0d7b43d 100755
--- a/tests/functional/test_sparc64_tuxrun.py
+++ b/tests/functional/test_sparc64_tuxrun.py
@@ -24,6 +24,7 @@ class TuxRunSparc64Test(TuxRunBaselineTest):
         '479c3dc104c82b68be55e2c0c5c38cd473d0b37ad4badccde4775bb88ce34611')
 
     def test_sparc64(self):
+        self.set_machine('sun4u')
         self.root='sda'
         self.wait_for_shutdown=False
         self.common_tuxrun(kernel_asset=self.ASSET_SPARC64_KERNEL,