Merge branch 'selftests-bpf-impose-global-ordering-for-test-decl_tags'

Merge branch 'selftests-bpf-impose-global-ordering-for-test-decl_tags'

Eduard Zingerman says:

====================
selftests/bpf: impose global ordering for test decl_tags

Impose global ordering for all decl tags used by test_loader.c based
tests: __success, __failure, __msg, etc. The tags are now sorted by
testing framework to be processed in the same order they appear in the
C source code of the test.

The ordering is necessary for gcc-bpf. Neither GCC nor the C standard
defines the order in which function attributes are consumed.
While Clang tends to preserve tags definition order in the output BTF,
GCC does not. This inconsistency causes BPF tests with multiple __msg
entries to fail when compiled with GCC.

This is based on a patch [1] from Cupertino Miranda (see patch #3) and
includes some additional cleanups for test_loader.c decl tags
declaration and processing (see patches #1, #2, #4).

[1] https://lore.kernel.org/bpf/20260305130035.192080-1-cupertino.miranda@oracle.com/

Changelog:
v2: https://lore.kernel.org/bpf/20260330-selftests-global-tags-ordering-v2-0-c0ac61e81098@gmail.com/
v2 -> v3:
- fixed free(tmp) call in collect_decl_tags() (Puranjay, bot)
- naming nit in compile_regex() (Mykyta)

v1 -> v2:
- refactoring str_has_pfx() usages missing from v1 (Puranjay)
- removed realloc_or_free() (Andrii)
- fixed qsort(NULL, ...) usage (Puranjay)
- skip_decl_tag_pfx() returns NULL if tag does not start from
  "comment:" (Puranjay)

v1: https://lore.kernel.org/bpf/20260326-selftests-global-tags-ordering-v1-0-5dd2ced5d9ad@gmail.com/
====================

Link: https://patch.msgid.link/20260410-selftests-global-tags-ordering-v2-0-c566ec9781bf@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>