Rework Nix infrastructure (and pick up more spurious failures)

This is based on the Nix Flake work. Let's get everything mainlined.

gitlab-bot/ghc_perf_import_service/__init__.py

@@ -120,7 +120,7 @@ class GHCPerfWebhookServer(WebhookServer):
         # Run eventlog import tool
         logging.info('Importing eventlog heap statistics')
         cmd = ['perf-import-head-hackage-eventlog']
-        cmd += [tmp_dir / 'eventlogs']
+        cmd += [str(tmp_dir / 'eventlogs')]
         cmd += [commit]
         cmd += [str(job.get_id())]
         cmd += [self.conn_string]
@@ -139,7 +139,7 @@ class GHCPerfWebhookServer(WebhookServer):
         cmd = ['perf-import-cabal']
         cmd += ['-i', str(job.get_id()) ]
         cmd += ['-c', self.conn_string]
-        cmd += [tmp_dir / 'out']
+        cmd += [str(tmp_dir / 'out')]
         subprocess.run(cmd, check=True)
 
     def _fetch_head_hackage_artifacts(self, job: ProjectJob, out_dir: Path):
@@ -209,7 +209,10 @@ class GHCPerfWebhookServer(WebhookServer):
         if grep(b'Idle CPU consumption too different'):
             joblog('T16916 failed')
             failures.append('T16916')
-        if grep(b'Cannot allocate memory'):
+        if (grep(b'Cannot allocate memory')
+                or grep(b'osCommitMemory: VirtualAlloc MEM_COMMIT failed')
+                or grep(b'out of memory allocating \d+ bytes')
+                ):
             joblog('could not allocate memory')
             failures.append('cannot_allocate')
         if grep(b'MoveFileEx'):