[audacity-freeworld] fix mp3importexport conditional.

[Kevin Kofler]

Sérgio Basto wrote:
> bcond_with and bcond_without are pretty easy to use and works well, I
> (personally) don't understand why we have another variants.

Because bcond_with and bcond_without have one major flaw: They are 
"backwards" compared to how most people think.

"%bcond_with foo" actually means to build WITHOUT foo by default, and to add 
a "--with foo" switch to build with foo. Likewise, "%bcond_without foo" 
actually means to build WITH foo by default, and to add a "--without foo" 
switch to build without foo. Many packagers find that really confusing.

And the --with and --without switches cannot be used in Koji anyway, so you 
may as well hardcode the options in the specfile using %global.

        Kevin Kofler