Wasm testsuite failure: compact_share

When testing with unregisterised codegen, compact_share passes with perf flavour but fails with user flavour that sets -O0 on stage1 libs:

--- "/tmp/tmp.cCNg1XZUj0/ghctest-364ofs86/test   spaces/libraries/ghc-compact/tests/compact_share.run/compact_share.stdout-ws-32.normalised"	2023-01-23 15:27:45.157418009 +0000
+++ "/tmp/tmp.cCNg1XZUj0/ghctest-364ofs86/test   spaces/libraries/ghc-compact/tests/compact_share.run/compact_share.run.stdout.normalised"	2023-01-23 15:27:45.158418012 +0000
@@ -1,4 +1,4 @@
 411963
-2588672
+2719744
 411963
-1343488
+1474560

This looks like a bug, since regardless of optimization level, the fully evaluated maps in https://gitlab.haskell.org/ghc/ghc/-/blob/master/libraries/ghc-compact/tests/compact_share.hs should have the same heap layout, therefore compactSize should be the same in both cases.