asterisk16: build native results in broken binaries under under certain circumstances

[Matthias Petermann <mp%petermann-it.de@localhost>]

Hello together,

last night I stumbled across a funny effect that might be interesting 
for one or the other Asterisk user as well.

Under certain circumstances the pkgbuild of Asterisk creates binaries 
that are not executable on other computers of the same upper 
architecture. This can be recognized by the fact that Asterisk crashes 
with "Illegal Instruction" at startup.

A typical backtrace looks like this:

```
Starting program: /usr/pkg/sbin/asterisk

Program received signal SIGILL, Illegal instruction.
0x00000000005d43cd in cfmtime_new (who_asked=0x624222 "", 
filename=0x7f7fff3bccb0 "/usr/pkg/etc/asterisk/asterisk.conf")
    at config.c:1567
1567    config.c: No such file or directory.
(gdb) bt
#0  0x00000000005d43cd in cfmtime_new (who_asked=0x624222 "", 
filename=0x7f7fff3bccb0 "/usr/pkg/etc/asterisk/asterisk.conf")
    at config.c:1567
#1  config_text_file_load (database=<optimized out>, table=<optimized 
out>, filename=<optimized out>, cfg=0x70384d489000,
    flags=..., suggested_include_file=0x624222 "", who_asked=0x624222 
"") at config.c:2147
#2  0x00000000005d3453 in ast_config_internal_load (
    filename=filename@entry=0x8d3700 <cfg_paths+11264> 
"/usr/pkg/etc/asterisk/asterisk.conf", cfg=cfg@entry=0x70384d489000,
    flags=flags@entry=..., 
suggested_include_file=suggested_include_file@entry=0x624222 "",
    who_asked=who_asked@entry=0x624222 "") at config.c:3142
#3  0x00000000005d6219 in ast_config_load2 (filename=0x8d3700 
<cfg_paths+11264> "/usr/pkg/etc/asterisk/asterisk.conf",
    who_asked=who_asked@entry=0x624222 "", flags=flags@entry=...) at 
config.c:3163
#4  0x0000000000510e71 in load_asterisk_conf () at options.c:232
#5  0x000000000061baa3 in main (argc=<optimized out>, 
argv=0x7f7fff3c0e48) at asterisk.c:3551
(gdb)
```

I was able to sufficiently identify the problem with this bug report:


https://community.asterisk.org/t/solved-illegal-instruction-error-after-ec2-instance-is-launched/76213

From this, it appears that Asterisk applies optimizations by default to 
the architecture on which it is built when creating binaries. Obviously, 
this causes these binaries to no longer run everywhere. In my case, the 
build system was a Xen VM running on a Xen host on an AMD FX-8350 
system. The kernels in each case are NetBSD 9.1. The binary was then 
supposed to run on an Intel NUC5 with a Celeron processor, which failed.

The possibility of occurrence of this problem is known and described in 
Asterisk. Disabling native builds is mentioned as a possible solution:


https://wiki.asterisk.org/wiki/display/AST/Building+and+Installing+Asterisk#BuildingandInstallingAsterisk-Buildingfornon-nativearchitectures

Since we are very particular about platform independence in NetBSD and 
pkgsrc, would it make sense to disable the native optimizations for 
Asterisk by default? I don't know how many people use Asterisk from the 
official pkg binaries, but chances are that there are regular systems 
out there that don't run it in this form. Also for people who build 
their own pkg repository the current behavior might be an unpleasant 
surprise.

In options.mk I didn't find any prepared switches for this for now. I'll 
try to add one and get back to you with a patch if necessary. If this 
already exists, I would be glad about a short message.

Kind regards
Matthias