[ELF] Drop const qualifier to fix -Wrange-loop-analysis. NFC

[MaskRay]

Summary

lld/ELF/Relocations.cpp:1622:56: warning: loop variable 'ts' of type 'const std::pair<ThunkSection *, uint32_t>' (aka 'const pair<lld::elf::ThunkSection *, unsigned int>') creates a copy from type 'const std::pair<ThunkSection *, uint32_t>' [-Wrange-loop-analysis]
        for (const std::pair<ThunkSection *, uint32_t> ts : isd->thunkSections)

Drop const qualifier to fix -Wrange-loop-analysis.
We can make -Wrange-loop-analysis warnings on const A more permissive on more
types (e.g. POD -> trivially copyable), unfortunately it will not make std::pair good,
because constexpr pair& operator=(const pair& p); is unfortunately user-defined.

[Mordante]

LGTM
I proposed the same change in D72210, but I'll adjust that patch once accepted.

[merge_guards_bot]

Unit tests: pass. 61247 tests passed, 0 failed and 736 were skipped.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: pass.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

lld/ELF/Relocations.cpp

forEachInputSectionDescription(
                        [](const std::pair<ThunkSection *, uint32_t> &ts) {
                          return ts.first->getSize() == 0;
                        });
 
         // ISD->ThunkSections contains all created ThunkSections, including
         // those inserted in previous passes. Extract the Thunks created this
         // pass and order them in ascending outSecOff.
         std::vector<ThunkSection *> newThunks;
-        for (const std::pair<ThunkSection *, uint32_t> ts : isd->thunkSections)
+        for (std::pair<ThunkSection *, uint32_t> ts : isd->thunkSections)
           if (ts.second == pass)
             newThunks.push_back(ts.first);
         llvm::stable_sort(newThunks,
                           [](const ThunkSection *a, const ThunkSection *b) {
                             return a->outSecOff < b->outSecOff;
                           });
 
         // Merge sorted vectors of Thunks and InputSections by outSecOff