testing/broot: check if x86 can be enabled again

It fails to build since the last update:

note: /usr/lib/gcc/i586-alpine-linux-musl/9.2.0/../../../../i586-alpine-linux-musl/bin/ld: /tmp/rustclvHfVF/liblibgit2_sys-c1839c55229d18b6.rlib(refs.o): in function `git_reference_normalize_name':
          refs.c:(.text.git_reference_normalize_name+0xae): undefined reference to `__stack_chk_fail_local'

This has to do with ld being used as a linker. It needs to be passed -lssp_nonshared for this to work.