[PPC] Segmentation fault instead of ReadOnlyMemoryException

[vchuravy]

      From worker 81:
      From worker 81:   signal (11): Segmentation fault
      From worker 81:   in expression starting at /autofs/nccsopen-svm1_home/vchuravy/builds/julia/usr/share/julia/stdlib/v1.3/Mmap/test/runtests.jl:98

[vchuravy]

s = open(file, "r")
m = Mmap.mmap(s)
@test_throws ReadOnlyMemoryError m[5] = UInt8('x') # tries to setindex! on read-only array
finalize(m); m=nothing; GC.gc()

So instead of a ReadOnlyMemoryError we get a segmentation fault.

[vchuravy]

On PPC we enter the signal handler with SEGV_MAPERR in info->si_code instead of the expected SEGV_ACCERR