[AIX] Update rpath for BUILD_SHARED_LIBS

[AIX] Update rpath for BUILD_SHARED_LIBS

BUILD_SHARED_LIBS build llvm component as shared library,
which can reduce the size a lot.

Normally, the binary use ORIGIN../lib to load component libraries,
unfortunatly, ORIGIN is not supported by AIX ld.

We hardcoded the build lib and install lib path in rpath for now
to enable BUILD_SHARED_LIBS build.

Understand that this is not perfect solution,
we can update this when we find better solution.

Reviewed By: hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D98901