Look in /etc/ld.so.conf and see if the directory that contains libproj.so.12 is in there?
the catch-22 is, /etc/ld.so.conf is a global thing, and this guy is building all his stuff to run under his /home/username/.... (where, btw, selinux might get unhappy with you). instead, if its private stuff like that, use LD_LIBRARY_PATH in the environment of the processes that need the libraries. or link with the paths hard coded, eg -Wl,-rpath=/home/username/..../lib64 when linking the packages that refer to these libraries.
Well when I did my build I also did some of it in my /home directory to replicate the OP's process to a certain extent. To get everything to run I symlinked the *.so's into the corresponding global directory covered by ld.so.config and ran ldconfig. Then all was golden. Before that I got similar error messages when CREATEing the postgis extension.
