Remove $FreeBSD$: one-line sh pattern

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

tests: Test libexecinfo backtrace call througth signal trampoline

It should fails on Aarch64 until https://reviews.llvm.org/D155066
is not merged.

Reviewed by:
Differential Revision: https://reviews.freebsd.org/D41129

libexecinfo test: Don't strip installed test

It turns out that a test of backtrace symbol resolution and formatting
requires symbols. Another option mightt be building with -rdynamic instead,
but this works for now.

Re-enabled skipped CI test, as it should now pass.

PR: 241562
Submitted by: lwhsu
Reported by: lwhsu
X-MFC-With: r354126, r354135, r354144

libexecinfo: Integrate NetBSD test into FreeBSD