using ldconfig and ld.so.conf versus LD_LIBRARY_PATH

I often build various libraries from source code to play with, such as gmp-6.1.2, mpfr-4.0.1, and gcc-7.x. In doing so, I prefer to use --prefix=/usr/local/gcc-7.2.0 so I know exactly where it is installed and does not mess up existing libraries. And then I all I basically know is what make install tells me at the end, to update or set LD_LIBRARY_PATH and sometimes but not always LD_RUN_PATH. most of the time I just manually set LD_LIBRARY_PATH as needed later on, or set it globally in something like /etc/bash.bashrc.local and that has worked. This is what make install says: Libraries have been installed in: /usr/local/mfprtest/lib If you ever happen to want to link against installed libraries in a given directory, LIBDIR, you must either use libtool, and specify the full pathname of the library, or use the '-LLIBDIR' flag during linking and do at least one of the following: - add LIBDIR to the 'LD_LIBRARY_PATH' environment variable during execution - add LIBDIR to the 'LD_RUN_PATH' environment variable during linking - use the '-Wl,-rpath -Wl,LIBDIR' linker flag - have your system administrator add LIBDIR to '/etc/ld.so.conf' See any operating system documentation about shared libraries for more information, such as the ld(1) and ld.so(8) manual pages. Is there a better way, **or a more offical way?** of using ldconfig and ld.so.conf than using LD_LIBRARY_PATH and LD_RUN_PATH, and PATH? This is specifically for writing my own code, but could be for other users, where I want to link against various newer versions of a library than what's installed with a given linux version, such as gmp, mpfr, and then using various manually installed versions of gcc such as gcc-5.x or gcc-6.x or gcc-7.x. basically, once I install /usr/local/gcc-7.3.0 for example, I want myself and any other user who either writes or runs home grown c, c++, or fortran source code on the system to use /usr/local/gcc-7.3.0 and not the system versions in /usr/bin/ and /usr/lib64/