In principle the KEEP command in your command file should do this.
From the GNU ld manual:
3.6.4.4 Input Section and Garbage Collection
When link-time garbage collection is in use (‘--gc-sections’), it is often useful to marksections that should not be eliminated. This is accomplished bysurrounding an input section’s wildcard entry with KEEP(), as inKEEP((.init)) or KEEP(SORT_BY_NAME()(.ctors)).
This SO answer contains an example of KEEP use that might help.
