NovaDiskIO still checks CPP11

[AdrianBunk]

While looking at commit 23fb31a I noticed https://github.com/supercollider/sc3-plugins/blob/main/source/NovaDiskIO/CMakeLists.txt#L3

This might be fixable with the below (untested) since this seems to have intended to force C++11 for not getting an older version:

-if(CPP11 AND NOT(SNDFILE MATCHES -NOTFOUND) )
+if( NOT(SNDFILE MATCHES -NOTFOUND) )

Looking at #239 I am not sure whether fixing or removal is the better option.

@JordanHendersonMusic

[dyfer]

Thanks @AdrianBunk
My understanding is that NovaDiskIO is not actively used - there's neither need nor purpose for it, AFAIU. I'd just let this be as is...