Intercept the RTLD to make library substitutions

To build on Titan/Chester

module switch PrgEnv-pgi PrgEnv-gnu
module load boost
module load cmake3

mkdir build && cd build
cmake -DCMAKE_INSTALL_PREFIX=/foo/bar -DCMAKE_BUILD_TYPE=RELEASE ..
make
make install

To use

If we want to intercept the dynamic loading of any library entry containing libfoo.so and replace it with /bar/libbar.so we can do the following

export RTLD_SUBSTITUTIONS=libfoo.so:/bar/libbar.so
LD_AUDIT='/install/prefix/libdl-intercept.so' a.out

multiple libraries can be intercepted by seperating the replacement pairs with a comma:

export RTLD_SUBSTITUTIONS=libfoo.so:/bar/libbar.so, libbaz.so:/raz/libraz.so

alternatively an absolute file path may be passed to RTLD_SUBSITUTIONS with one substitution pair per line

export RTLD_SUBSTITUTIONS=/full/path/subs.conf
cat /full/path/subs.conf
libfoo.so : /bar/libbar.so
libbaz.so : /raz/libraz.so