Since merge of kf5 branch, lost the effective modifcation from past commit https://cgit.kde.org/libkcddb.git/commit/cmake/FindMusicBrainz5.cmake?id=a6ef64de33a84d4842659241d8bda3b12190f8ca to support (multiple) include dirs, so builds will effectively use $ pkg-config --cflags libmusicbrainz5 (output on my box includes: -I/usr/include/neon -I/usr/include/libxml2 ) I noticed this primarily because libkcddb fails to build on RHEL7 without that.
Or can just live with this and require libmusticbrainz >= 5.1 where the strict dependency on libxml2 was dropped. (And I can just workaround it downstream by manually adding include dirs as needed)
Would include_directories(${MUSICBRAINZ5_INCLUDE_DIRS}) help when MUSICBRAINZ5_FOUND?