Used by alsa-lib to register symbol list for fake dlsym.
Would require support from QBE, maybe just to specify section of global data.
pixman also uses this, but has fallback code for systems that don't support it.
However, since we currently define away all attributes (#68), we cannot detect support for this with just a compile test. Once #68 is resolved, we can ignore some attributes and error on others, so that a compile test would be sufficient.