I reported this upstream: https://github.com/hercules-team/augeas/issues/768

During package builds and during development phase, openSUSE sets
MALLOC_CHECK_=3 and MALLOC_PERTURB_=69 in the environment. This causes the
glibc heap to be less "forgiving" to catch some bugs.

However, the MALLOC_PERTURB_=69 setting, which causes glibc to explicitly fill
newly allocated and freed memory with that value, has a massive negative effect
on augeas performance. The testsuite actually runs more than 20x slower!
Effectively, the package build takes >2000s instead of 99s because of this.

FWICT, the bottleneck is that add_new_trans calls realloc very often, and glibc
treats that like a new allocation + deallocation to be able to overwrite the
old data. Maybe that can be optimized somehow?

perf report shows:

-   95,52%     0,00%  augparse  libaugeas.so.0.25.0   [.] typecheck             
     typecheck                                                                  
     typecheck_iter                                                             
   - ambig_iter_check                                                           
      - 94,70% ambig_check                                                      
         - fa_ambig_example                                                     
            - 84,24% expand_alphabet (inlined)                                  
               - 84,23% fa_clone                                                
                  - 83,90% add_new_trans                                        
                     - mem_realloc_n                                            
                        - 83,88% __realloc (inlined)                            
                           - _int_realloc                                       
                              - 83,87% _int_free                                
                                   __memset_avx2_unaligned_erms

needinfo on glibc to confirm that the suspicion is true.

Maybe we should just unset _MALLOC_PERTURB in augeas.spec's %check section?