(PA-4871) Add our libdir to the runtime linker search path

[joshcooper]

When the runtime linker loads executables, it uses a search path in the
executable to find library dependencies. On most platforms this is done
via -rpath, but on AIX it's -R. The search path is embedded in the
executable and can be seen using:

# dump -H /opt/puppetlabs/puppet/bin/openssl
...
                           ***Import File Strings***
INDEX  PATH                          BASE                MEMBER
0      /opt/puppetlabs/puppet/lib:/usr/lib:/lib

Built in https://jenkins-platform.delivery.puppetlabs.net/view/vanagon-generic-builder/job/platform_vanagon-generic-builder_vanagon-packaging_generic-builder/2110/BUILD_TARGET=aix-7.2-ppc,SLAVE_LABEL=k8s-worker/

Project agent-runtime-main

Platform name: aix-7.2-ppc

Component 'openssl-3.0'

        Field: environment

- CC=/opt/freeware/bin/gcc CFLAGS=-I/opt/puppetlabs/puppet/include -I/opt/pl-build-tools/include -static-libgcc LDFLAGS=-Wl,-brtl -L/opt/puppetlabs/puppet/lib -latomic -lm
+ CC=/opt/freeware/bin/gcc CFLAGS=-I/opt/puppetlabs/puppet/include -I/opt/pl-build-tools/include -static-libgcc LDFLAGS=-Wl,-brtl -L/opt/puppetlabs/puppet/lib -Wl,-R/opt/puppetlabs/puppet/lib -latomic -lm