This looks like a 64- vs. 32-bit lib directory problem.

There are generally two types of mixed 64/32-bit Linux distros: one type puts the 'native' 64-bit libs in /usr/lib etc., and the old 32-bit libs in some 'compat' directory, typically /usr/lib32. The other puts the 64-bit libs in /usr/lib64 etc., and leaves the old 32-bit libs in /usr/lib. Everything else in the system is compiled and set up such that the appropriate lib directories are being searched by 64- and 32-bit binaries respectively. Both approaches have their pros and cons, which is why you find them both...

Your system looks like the second type. In other words, if your self-built libiconv.so.2 is in fact 64-bit (as it seems to be, otherwise using LD_LIBRARY_PATH wouldn't have helped), it should actually live in a directory with '64' in its name (e.g. /usr/lib64).

PS: you can check 64/32-bitness with file -L /usr/lib/libiconv.so.2