TestSharedSnapshotConcurrentIntegrity writes as fast as one core can
marshal for two seconds, so its transient heap scales with host speed.
On linux/386 a fast runner walks the heap into the 4GB address-space
ceiling and the run dies with out of memory. Set a 1GB memory limit for
the duration of the test so the GC paces the writer instead of the
address space; the seal-and-recycle race being tested is unaffected.
Chris LuandGitHub
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