[NFC][AIX][XCOFF] fixed compile warning on the strncpy.

[DiggerLin]

Summary

There is warning when compile the file XCOFFObjectWriter.cpp
/srv/llvm-buildbot-srcatch/llvm-build-dir/openmp-gcc-x86_64-linux-debian/llvm.src/llvm/lib/MC/XCOFFObjectWriter.cpp:414:17: warning: 'char* strncpy(char*, const char*, size_t)' specified bound 8 equals destination size [-Wstringop-truncation]

the patch fixed the warning.

[daltenty]

LGTM (previous discussion in D70859)

[hubert.reinterpretcast]

llvm/lib/MC/XCOFFObjectWriter.cpp

419

@DiggerLin, please add a comment that the buffer size is adjusted to avoid a false-positive compiler warning.

llvm/lib/MC/XCOFFObjectWriter.cpp

bool XCOFFObjectWriter::nameShouldBeInStringTable(const StringRef &SymbolName) {
   return SymbolName.size() > XCOFF::NameSize;
 }
 
 void XCOFFObjectWriter::writeSymbolName(const StringRef &SymbolName) {
   if (nameShouldBeInStringTable(SymbolName)) {
     W.write<int32_t>(0);
     W.write<uint32_t>(Strings.getOffset(SymbolName));
   } else {
-    char Name[XCOFF::NameSize];
+    char Name[XCOFF::NameSize+1];
     std::strncpy(Name, SymbolName.data(), XCOFF::NameSize);
     ArrayRef<char> NameRef(Name, XCOFF::NameSize);
     W.write(NameRef);
   }
 }
 
 void XCOFFObjectWriter::writeSymbolTableEntryForCsectMemberLabel(
     const Symbol &SymbolRef, const ControlSection &CSectionRef,