bootstrap: try better workaround for builds on Linux/HPPA
The workaround currently present works fine without -O or with -O1, but fails with -Os or -O2 and higher. Using -O2 is common e.g. in Gentoo, as resulting in bugs like this: https://bugs.gentoo.org/473276 Prevent the workaround for higher optimization levels to make bootstrapping more likely to succeed. This is still a workaround as ld still keeps crashing in some situations.