tests: Don't build securityselinuxlabeltest without qemu

Sources for securityselinuxlabeltest are only defined if qemu driver is
enabled so we should not try to build the test if qemu driver is
disabled.

tests/Makefile.am

@@ -108,10 +108,12 @@ endif
 
 if WITH_SECDRIVER_SELINUX
 test_programs += securityselinuxtest
+if WITH_QEMU
 if WITH_ATTR
 test_programs += securityselinuxlabeltest
 endif
 endif
+endif
 
 if WITH_DRIVER_MODULES
 test_programs += virdrivermoduletest