AIX: Fix INSTALL_REMOVE_ENVIRONMENT_RPATH with GNU compiler

Since commit baa33acbda (AIX-GNU: Put implicit link directories in
runtime libpath, 2013-02-14, v2.8.11~184^2~1) we explicitly add the GNU
compiler driver's builtin RPATH entries.  Extend commit f08dcbffec
(Property: Add INSTALL_REMOVE_ENVIRONMENT_RPATH property, 2019-07-12,
v3.16.0-rc1~350^2~1) to exclude them.

Fixes: #27738