This disables a workaround only intended for aarch64 if the target
architecture is powerpc.

Issue: #3365

../contrib/libev/ev.c: In function ‘ev_io_start’:
../contrib/libev/ev.c:4396:34: warning: suggest parentheses around arithmetic in operand of ‘|’ [-Wparentheses]
 4396 |   fd_change (EV_A_ fd, w->events & EV__IOFDSET | EV_ANFD_REIFY);
      |                        ~~~~~~~~~~^~~~~~~~~~~~~

../contrib/libev/ev.c: At top level:
../contrib/libev/ev.c:5660:27: warning: "/*" within comment [-Wcomment]
 5660 | /* EV_STAT     0x00001000 /* stat data changed */
      |
../contrib/libev/ev.c:5661:27: warning: "/*" within comment [-Wcomment]
 5661 | /* EV_EMBED    0x00010000 /* embedded event loop needs sweep */
      |

GCC does not respect `(void) func()`

723d9c8486 in replxx's git.

Building rspamd with gcc10 errors out with "'runtime_error' is not a
member of 'std'" otherwise.

Issue: #3317

This reverts commit b05b9bf904.

Changelog: http://cvs.schmorp.de/libev/Changes?pathrev=rel-4_33

* Reproducible builds! No more absolute paths in source files, so the
  generated binary is also invariant of the build directory.
* Output modules.h in snowball/libstemmer/ instead of snowball/. This
  allows removal of the extra include directory and -f option.
* This partially reverts some changes in
  d178f201fd
  and matches the commands in GNUmakefile.

* Avoid including the absolute header path to permit reproducible builds
  invariant of the build direvtory.

[74/340] Building C object contrib/lua-lpeg/CMakeFiles/rspamd-lpeg.dir/lpprint.c.o
In file included from ../contrib/lua-lpeg/lpprint.c:11:
../contrib/lua-lpeg/lptypes.h:15: warning: "NDEBUG" redefined
   15 | #define NDEBUG
      |
<command-line>: note: this is the location of the previous definition
[75/340] Building C object contrib/lua-lpeg/CMakeFiles/rspamd-lpeg.dir/lpcap.c.o
In file included from ../contrib/lua-lpeg/lpcap.h:9,
                 from ../contrib/lua-lpeg/lpcap.c:9:
../contrib/lua-lpeg/lptypes.h:15: warning: "NDEBUG" redefined
   15 | #define NDEBUG
      |
<command-line>: note: this is the location of the previous definition
[77/340] Building C object contrib/lua-lpeg/CMakeFiles/rspamd-lpeg.dir/lpvm.c.o
In file included from ../contrib/lua-lpeg/lpcap.h:9,
                 from ../contrib/lua-lpeg/lpvm.c:15:
../contrib/lua-lpeg/lptypes.h:15: warning: "NDEBUG" redefined
   15 | #define NDEBUG
      |
<command-line>: note: this is the location of the previous definition
[79/340] Building C object contrib/lua-lpeg/CMakeFiles/rspamd-lpeg.dir/lpcode.c.o
In file included from ../contrib/lua-lpeg/lpcode.c:12:
../contrib/lua-lpeg/lptypes.h:15: warning: "NDEBUG" redefined
   15 | #define NDEBUG
      |
<command-line>: note: this is the location of the previous definition
[81/340] Building C object contrib/lua-lpeg/CMakeFiles/rspamd-lpeg.dir/lptree.c.o
In file included from ../contrib/lua-lpeg/lptree.c:15:
../contrib/lua-lpeg/lptypes.h:15: warning: "NDEBUG" redefined
   15 | #define NDEBUG
      |
<command-line>: note: this is the location of the previous definition

../contrib/snowball/compiler/analyser.c: In function ‘check_name_type’:
../contrib/snowball/compiler/analyser.c:210:19: warning: this ‘if’ clause does not guard... [-Wmisleading-indentation]
  210 |         case 'r': if (p->type == t_routine ||
      |                   ^~
../contrib/snowball/compiler/analyser.c:211:54: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘if’
  211 |                       p->type == t_external) return; break;
      |                                                      ^~~~~
../contrib/snowball/compiler/analyser.c: In function ‘read_program’:
../contrib/snowball/compiler/analyser.c:859:21: warning: this ‘if’ clause does not guard... [-Wmisleading-indentation]
  859 |                     if (q->used && q->definition == 0) error4(a, q); break;
      |                     ^~
../contrib/snowball/compiler/analyser.c:859:70: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘if’
  859 |                     if (q->used && q->definition == 0) error4(a, q); break;
      |                                                                      ^~~~~
../contrib/snowball/compiler/analyser.c:861:21: warning: this ‘if’ clause does not guard... [-Wmisleading-indentation]
  861 |                     if (q->used && q->grouping == 0) error4(a, q); break;
      |                     ^~
../contrib/snowball/compiler/analyser.c:861:68: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘if’
  861 |                     if (q->used && q->grouping == 0) error4(a, q); break;
      |                                                                    ^~~~~