[BOLT] Add nfc-check-validation step (#462)

NFC-mode runs in-tree and out-of-tree (large BOLT tests) when there are
changes
affecting llvm-bolt between the current revision and the previous one.

However, the revision SHA itself and the GNU build-id may be two unique
differences when doing such a comparison.

This patch introduces a lightweight sanity check step that reports a
warning on
the Buildbot so that we are aware when this occurs.

Author: paschalis-mpeis

zorg/buildbot/builders/BOLTBuilder.py

@@ -1,4 +1,5 @@
 from buildbot.plugins import steps
+from buildbot.process.results import SUCCESS, FAILURE, WARNINGS
 from buildbot.steps.shell import ShellCommand
 from zorg.buildbot.builders.UnifiedTreeBuilder import getLLVMBuildFactoryAndSourcecodeSteps, addCmakeSteps, addNinjaSteps
 from zorg.buildbot.commands.LitTestCommand import LitTestCommand
@@ -92,6 +93,26 @@ def getBOLTCmakeBuildFactory(
                 haltOnFailure=False,
                 flunkOnFailure=False,
                 env=env),
+            ShellCommand(
+                name='nfc-check-validation',
+                command=(
+                    "info=$(bin/llvm-bolt.new --version | grep 'BOLT revision' "
+                    "| grep -q '<unknown>' || echo 'bolt-revision'); "
+                    "info=$info$(readelf --notes bin/llvm-bolt.new "
+                    "| grep -q 'Build ID:' && echo ' GNU-build-id'); "
+                    "info=$(echo \"$info\" | sed 's/^ //'); "
+                    "[ ! -z \"$info\" ] || return 0 && "
+                    "(printf \"NFC-Mode WARNING: unique IDs found in binaries ($info)"
+                    ". This means tests will run at all times.\"; return 2)"
+                    ),
+                description=('Check that nfc-mode works as intended when '
+                             'comparing with the previous commit.'),
+                haltOnFailure=False,
+                warnOnFailure=True,
+                warnOnWarnings=True,
+                decodeRC={0: SUCCESS, 1: FAILURE, 2: WARNINGS},
+                descriptionDone=["NFC-Mode unique IDs in binaries"],
+                env=env),
             ShellCommand(
                 name='check-bolt-different',
                 command=('find -name timing.log -delete; '