Configure GCC with --enable-default-pie

Due to ASLR security hardening, most Linux distributions have switched to default PIE for their GCC builds for many years. Actually I cannot find a Linux distribution which doesn't use default PIE. See https://gist.github.com/thesamesam/f7a9c17df0165e86babb189fda8d3048 for a survey.

Many GCC build scripts like https://github.com/richfelker/musl-cross-make , glibc `scripts/build-many-glibcs.py` specify `--enable-default-pie` as well.

At this point, I think it makes more sense for compiler-explorer to match the Linux status quo, rather than the upstream default.

GCC feature request about switching the default for Linux: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103398

Review the repository's GCC build configuration and identify where compiler configure options are defined. Compare the current settings with the --enable-default-pie examples in musl-cross-make and glibc's scripts/build-many-glibcs.py, then verify that the generated GCC builds use the requested default PIE behavior.

Written by the indexing model from the issue text.