[llvm] Silence warning when building with Clang ToT

This fixes:
```
[1343/7452] Building CXX object lib\Object\CMakeFiles\LLVMObject.dir\ELFObjectFile.cpp.obj
C:\git\llvm-project\llvm\lib\Object\ELFObjectFile.cpp(808,27): warning: comparison of integers of different signs: 'unsigned int' and '_Iter_diff_t<const Elf_Shdr_Impl<ELFType<llvm::endianness::little, false>> *>' (aka 'int') [-Wsign-compare]
  808 |     if (*TextSectionIndex != std::distance(Sections.begin(), *TextSecOrErr))
      |         ~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\git\llvm-project\llvm\lib\Object\ELFObjectFile.cpp(913,12): note: in instantiation of function template specialization 'readBBAddrMapImpl<llvm::object::ELFType<llvm::endianness::little, false>>' requested here
  913 |     return readBBAddrMapImpl(Obj->getELFFile(), TextSectionIndex, PGOAnalyses);
      |            ^
```

Author: aganea

llvm/lib/Object/ELFObjectFile.cpp

@@ -805,7 +805,10 @@ Expected<std::vector<BBAddrMap>> static readBBAddrMapImpl(
       return createError("unable to get the linked-to section for " +
                          describe(EF, Sec) + ": " +
                          toString(TextSecOrErr.takeError()));
-    if (*TextSectionIndex != std::distance(Sections.begin(), *TextSecOrErr))
+    assert(*TextSecOrErr >= Sections.begin() &&
+           "Text section pointer outside of bounds");
+    if (*TextSectionIndex !=
+        (unsigned)std::distance(Sections.begin(), *TextSecOrErr))
       return false;
     return true;
   };