Remove stray architecture_independent export

This should have been removed with https://github.com/ros/diagnostics/commit/3c1da654a1a2e0d26d2c1e96b047220f13e52c57

Example build break: http://csc.mcs.sdsmt.edu/jenkins/job/ros-indigo-diagnostic-common-diagnostics_binaryrpm_heisenbug_i386/44/console