Remove $FreeBSD$: one-line .c comment pattern

Remove /^/[*/]\s*\$FreeBSD\$.*\n/

Revert 305098

Was a wrong assumption from me badly look at the errors cross toolchain was
telling me

Make libc++.so ldscript sysroot friendly

After r253839, which modifies ld's behaviour to not automatically pull
in needed libraries, change libc++.so into a linker script, so it can
automatically pull in libcxxrt.so.

MFC after: 1 week