oeqa/selftest/rust: skip on all MIPS platforms

As per "The rustc book"[1], mips*-unknown-linux-* are "tier 3" targets:

  Tier 3 targets are those which the Rust codebase has support for, but
  which the Rust project does not build or test automatically, so they
  may or may not work.

We already skip qemumips in this selftest, but we're now also seeing
failures with qemumips64 so refactor the test to skip all machines where
the architecture is mips or mips64.

[1] https://doc.rust-lang.org/nightly/rustc/platform-support.html

(From OE-Core rev: 177e268811c04260923ac4b16fa047315304add0)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/selftest/cases/rust.py

@@ -3,6 +3,7 @@ import os
 import subprocess
 import time
 from oeqa.core.decorator import OETestTag
+from oeqa.core.decorator.data import skipIfArch
 from oeqa.core.case import OEPTestResultTestCase
 from oeqa.selftest.case import OESelftestTestCase
 from oeqa.utils.commands import runCmd, bitbake, get_bb_var, get_bb_vars, runqemu, Command
@@ -38,15 +39,12 @@ def parse_results(filename):
 @OETestTag("toolchain-user")
 @OETestTag("runqemu")
 class RustSelfTestSystemEmulated(OESelftestTestCase, OEPTestResultTestCase):
+
+    @skipIfArch(['mips', 'mips64'])
     def test_rust(self, *args, **kwargs):
         # Disable Rust Oe-selftest
         #self.skipTest("The Rust Oe-selftest is disabled.")
 
-        # Skip mips32 target since it is unstable with rust tests
-        machine = get_bb_var('MACHINE')
-        if machine == "qemumips":
-            self.skipTest("The mips32 target is skipped for Rust Oe-selftest.")
-
         # build remote-test-server before image build
         recipe = "rust"
         start_time = time.time()