heapprof001 segfaults in prof_hc_hb way on i386

I am seeing the heapprof001 testcase segmentation fault in the prof_hc_hb testsuite way on i386. For instance, https://circleci.com/gh/ghc/ghc/7104:

Wrong exit code for heapprof001(prof_hc_hb)(expected 0 , actual 139 )
Stdout ( heapprof001 ):
a <= 
a <= 
a <= 
a <= 
a <= 
a <= 
a <=
Stderr ( heapprof001 ):
Segmentation fault
*** unexpected failure for heapprof001(prof_hc_hb)

Edited Mar 10, 2019 by Ben Gamari

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