Scripts/qa.sh: fine tune USES=ssl recommendation

[fernape]

Summary

Try to avoid the "you need USES=ssl" in ports that provide a libssl.so or
libcrypto.so libraries themselves as security/openssl or security/libressl.

Comes from PR270035

Test Plan

Apply patch and make openssl, libressl or other ssl ports.
If building other ports that don't provide those libraries by themselves, then
the warning still applies

[ngie]

[fernape]

Ping!

[fernape]

In D41973#965375, @fernape wrote:

Ping!

Another friendly Ping!

[fernape]

Friendly ping

[mat]

Mk/Scripts/qa.sh

140–146

As we don't need whatever list_stagedir_elfs outputs, maybe here tests its output directly, something like :

if list_stagedir_elfs ... | grep -q 'lib.*.so'; then
...

[fernape]

Address mat's feedback

[mat]

Mk/Scripts/qa.sh

118

This is not needed any more now.

140–146

I know I'm being pedantic but could you add an empty line between the EOF and the if ? (to ease reading)

[fernape]

Remove unused variable
Add empty line to improve readability

[fernape]

Thanks for the review