Support using LLVM as a disassembler method, allowing helperless
annotation in non-distro builds. (It is also much faster than
using libbfd or bfd objdump on binaries with a lot of debug
information.)

This is nearly identical to the output of llvm-objdump; there are
some very rare whitespace differences, some minor changes to demangling
(since we use perf's regular demangling and not LLVM's own) and
the occasional case where llvm-objdump makes a different choice
when multiple symbols share the same address.

It should work across all of LLVM's supported architectures, although
I've only tested 64-bit x86, and finding the right triple from perf's
idea of machine architecture can sometimes be a bit tricky. Ideally, we
should have some way of finding the triplet just from the file itself.

Committer notes:

Address this on 32-bit systems by using PRIu64 from inttypes.h

     3    17.58 almalinux:9-i386              : FAIL gcc version 11.4.1 20231218 (Red Hat 11.4.1-3) (GCC)
      util/llvm-c-helpers.cpp: In function ‘char* make_symbol_relative_string(dso*, const char*, u64, u64)’:
      util/llvm-c-helpers.cpp:150:52: error: format ‘%lx’ expects argument of type ‘long unsigned int’, but argument 5 has type ‘u64’ {aka
  +‘long long unsigned int’} [-Werror=format=]
        150 |                 snprintf(buf, sizeof(buf), "%s+0x%lx",
            |                                                  ~~^
            |                                                    |
            |                                                    long unsigned int
            |                                                  %llx
        151 |                          demangled ? demangled : sym_name, addr - base_addr);
            |                                                            ~~~~~~~~~~~~~~~~
            |                                                                 |
            |                                                                 u64 {aka long long unsigned int}
      cc1plus: all warnings being treated as errors
Signed-off-by: Steinar H. Gunderson <sesse@google.com>
Cc: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20240803152008.2818485-3-sesse@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>