Fix rtaudio build using internal copy.
Fix rtaudio build using internal copy.

j-b-m/mlt,j-b-m/mlt,j-b-m/mlt,mltframework/mlt,siddharudh/mlt,xzhavilla/mlt,mltframework/mlt,j-b-m/mlt,mltframework/mlt,siddharudh/mlt,mltframework/mlt,xzhavilla/mlt,j-b-m/mlt,mltframework/mlt,j-b-m/mlt,j-b-m/mlt,xzhavilla/mlt,xzhavilla/mlt,j-b-m/mlt,xzhavilla/mlt,xzhavilla/mlt,siddharudh/mlt,mltframework/mlt,xzhavilla/mlt,j-b-m/mlt,mltframework/mlt,mltframework/mlt,xzhavilla/mlt,siddharudh/mlt,mltframework/mlt,siddharudh/mlt,j-b-m/mlt,xzhavilla/mlt,siddharudh/mlt,siddharudh/mlt,siddharudh/mlt,siddharudh/mlt,mltframework/mlt