textproc/topic: fix build with GCC-based architectures

[pkubaj]

Summary

Remove -Werror to fix this:
./linenoise.c: In function 'linenoiseEdit':
./linenoise.c:765: warning: comparison is always false due to limited range of data type

With -Werror, it causes a build error on GCC architectures.

PR: 237555

[tcberner]

Not quite sure if that makes sense. Won't the compiled binary basically do garbage in this case?

[pkubaj]

Add specific signed to the variable. This solves the build issue.