[NFC][SpecialCaseList] Store SectionStr as StringRef (#167278)

The SectionStr is already copied in addSection, so
there is no need to copy it again in the Section
constructor.

Co-authored-by: Matt Arsenault <[email protected]>

Author: vitalybuka

llvm/include/llvm/Support/SpecialCaseList.h

@@ -232,7 +232,7 @@ class SpecialCaseList {
     findMatcher(StringRef Prefix, StringRef Category) const;
 
     Matcher SectionMatcher;
-    std::string SectionStr;
+    StringRef SectionStr;
     SectionEntries Entries;
     unsigned FileIdx;
   };

llvm/lib/Support/SpecialCaseList.cpp

@@ -243,10 +243,10 @@ bool SpecialCaseList::createInternal(const MemoryBuffer *MB, std::string &Error,
 Expected<SpecialCaseList::Section *>
 SpecialCaseList::addSection(StringRef SectionStr, unsigned FileNo,
                             unsigned LineNo, bool UseGlobs) {
+  SectionStr = SectionStr.copy(StrAlloc);
   Sections.emplace_back(SectionStr, FileNo, UseGlobs);
   auto &Section = Sections.back();
 
-  SectionStr = SectionStr.copy(StrAlloc);
   if (auto Err = Section.SectionMatcher.insert(SectionStr, LineNo)) {
     return createStringError(errc::invalid_argument,
                              "malformed section at line " + Twine(LineNo) +