We do not gain any additional security from having PIE on the test
binaries, and this does have an impact on test times. It is about 10%
from my measurements. Not as much as previous reports
(https://reviews.llvm.org/D140880), but still significant. This is a
similar gain to finish enabling the lit internal shell, which will take
significantly more effort. I also do not think this is a meaningful
enough difference from the "default" configuration to keep it the
default, especially given the option is mostly set by distros.
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