glibc ≥ 2.42 (GCC 15) defaults to -std=gnu23, which promotes
-Wdiscarded-qualifiers to an error in the default hardening flags
of Fedora Rawhide, Arch Linux, openSUSE Tumbleweed, Gentoo, etc.

In C23, strstr() and strchr() return "const char *" in most cases,
making previous implicit casts invalid.

This breaks the build of tools/bpf/resolve_btfids on pristine
upstream kernel when using GCC 15 + glibc 2.42+.

Fix the three remaining instances with explicit casts.

No functional changes.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=2417601
Suggested-by: Florian Weimer <redacted>
Signed-off-by: Mikhail Gavrilov <redacted>

---
v2:
- Declare `res` as `const char *` — never modified.
- Keep `sym_sfx` as `char *` and cast — it is advanced in the loop.
- Cast `next_path` — declared as `char *` earlier in the function.
  Changing it to const would require refactoring the whole function,
  which is not justified for a tools/ file.
---
 tools/lib/bpf/libbpf.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index dd3b2f57082d..22ccd50e9978 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -8245,7 +8245,7 @@ static int kallsyms_cb(unsigned long long sym_addr, char sym_type,
        struct bpf_object *obj = ctx;
        const struct btf_type *t;
        struct extern_desc *ext;
-       char *res;
+       const char *res;

        res = strstr(sym_name, ".llvm.");
        if (sym_type == 'd' && res)

@@ -11576,7 +11576,7 @@ static int avail_kallsyms_cb(unsigned long long sym_addr, char sym_type,
                 */
                char sym_trim[256], *psym_trim = sym_trim, *sym_sfx;

-               if (!(sym_sfx = strstr(sym_name, ".llvm.")))
+               if (!(sym_sfx = (char *)strstr(sym_name, ".llvm.")))  /* needs mutation */
                        return 0;

                /* psym_trim vs sym_trim dance is done to avoid pointer vs array

@@ -12164,7 +12164,7 @@ static int resolve_full_path(const char *file, char *result, size_t result_sz)

                        if (s[0] == ':')
                                s++;
-                       next_path = strchr(s, ':');
+                       next_path = (char *)strchr(s, ':');   /* declared as char * above */