Fix emulators/qemu-sbruno build with lld 10.0.0

As reported in bug 244251, with clang and lld 10.0.0 the emulators/qemu-sbruno port fails in the configure stage:

> Configuring for qemu-user-static-2.11.50.g20191211_3

ERROR: We need to link the QEMU user mode binaries at a

specific text address. Unfortunately your linker
doesn't support either the -Ttext-segment option or
printing the default linker script with --verbose.
If you don't want the user mode binaries, pass the
--disable-user option to configure.

> Script "configure" failed unexpectedly.

Please report the problem to emulation@FreeBSD.org [maintainer] and attach
the
"/wrkdirs/usr/ports/emulators/qemu-user-static/work/qemu-bsd-user-d587db6/config.log"
including the output of the failure of your make command. Also, it might be
a good idea to provide an overview of all packages installed on your system
(e.g. a /usr/local/sbin/pkg-static info -g -Ea).

• Error code 1

This is because lld 10.0.0 no longer supports the -Ttext-segment option, and uses --image-base for similar functionality.

I am proposing a patch that makes the configure script check for the --image-base option first, then the -Ttext-segment option.

PR: ports/244772
Submitted by: dim@FreeBSD.org
Approved by: Maintainer