CI: do not build SVF 2.4 with -Werror
CI: do not build SVF 2.4 with -Werror

... as it fails to compile without warning with GCC 11.2.0.  It's generally
a really bad idea to force -Werror onto your users exactly for this reason.

mchalupa/dg,mchalupa/dg,mchalupa/dg,mchalupa/dg