Sorry for the trouble. I realize since there is a new version of libmng2 along with updated libmng-dev on Debian experimental, applying the same fix (Install pkgconfig file) may not be needed in an older version.
Moreover, libmng package has been left dormant since 2018 https://tracker.debian.org/pkg/libmng Again, sorry for the trouble. PS: This bug was reported against the right package ie., libmng-dev and not libmng1. I'm new so a little bit of confusion I had there :)
