update travis clang
Seems clang-7 has false-positives around memory sanitizer.
This line should not be reported because the memory region is correctly unpoisoned beforehand: https://travis-ci.org/ruby/ruby/jobs/524766381
Clang 8 seems to fix it.
Added by shyouhei (Shyouhei Urabe) over 6 years ago
update travis clang
Seems clang-7 has false-positives around memory sanitizer.
This line should not be reported because the memory region is
correctly unpoisoned beforehand:
https://travis-ci.org/ruby/ruby/jobs/524766381
Clang 8 seems to fix it.