Add ALLOW_RETRIES to flaky test dbg-record-roundtrip.ll (llvm#85410)

Something strange is happening in this test.

If the llvm-as output is piped into llvm-link in the final RUN lines
then this test fails on my machine (1 in 200) using WSL2. If the
verify-uselistorder RUN lines are removed then it doesn't fail on my
machine (in 10,000+). If the llvm-as and llvm-link RUN lines mentioned
at the start are removed then it doesn't fail on my machine (in
10,000+).

Writing the llvm-as output to a temporary file for llvm-link to read on
those final RUN lines, the test doesn't fail on my machine (in 10,000+).
But it _does_ fail on a bot:
https://lab.llvm.org/buildbot/#/builders/245/builds/21930. So clearly my
workaround doesn't solve the underlying problem (and I have no idea what
that is).

Author: OCHyams

llvm/test/Bitcode/dbg-record-roundtrip.ll

@@ -17,6 +17,11 @@
 ;; NOTE: This test fails intermittently on linux if the llvm-as output is piped
 ;; into llvm-link in the RUN lines below, unless the verify-uselistorder RUN
 ;; lines above are removed. Write to a temporary file to avoid that weirdness.
+;; NOTE2: Unfortunately, the above only stopped it occuring on my machine.
+;; It failed again intermittently here:
+;; https://lab.llvm.org/buildbot/#/builders/245/builds/21930
+;; Allow this test to fail-over twice, until this strangeness is understood.
+; ALLOW_RETRIES: 2
 ; RUN: llvm-as %s --experimental-debuginfo-iterators=true --write-experimental-debuginfo-iterators-to-bitcode=true -o %t
 ; RUN: llvm-link %t %s --experimental-debuginfo-iterators=false -o /dev/null
 ; RUN: llvm-as %s --experimental-debuginfo-iterators=false -o %t