[lldb][NFC] Remove unnecessary std::string temporaries

The existing code was taking three substrings from a regex match and converting
to std::strings prior to using them. This may have been done to address
null-termination concerns, but this is not the case:

1. `name` was being used to call `c_str()` and then implicitly converted back to
a `StringRef` on the call to `ToAddress`. While the path `const char *` ->
`StringRef` requires null-termination, we can simply use the original StringRef.
2. `str_offset` was being converted back to a StringRef in order to call a
member method. Member methods can't handle non-null termination.
3. `sign` simply had it's 0-th element accessed.

Author: felipepiovezan

lldb/source/Interpreter/OptionArgParser.cpp

@@ -243,12 +243,12 @@ OptionArgParser::DoToAddress(const ExecutionContext *exe_ctx, llvm::StringRef s,
     llvm::SmallVector<llvm::StringRef, 4> matches;
     if (g_symbol_plus_offset_regex.Execute(sref, &matches)) {
       uint64_t offset = 0;
-      std::string name = matches[1].str();
-      std::string sign = matches[2].str();
-      std::string str_offset = matches[3].str();
-      if (!llvm::StringRef(str_offset).getAsInteger(0, offset)) {
+      llvm::StringRef name = matches[1];
+      llvm::StringRef sign = matches[2];
+      llvm::StringRef str_offset = matches[3];
+      if (!str_offset.getAsInteger(0, offset)) {
         Status error;
-        addr = ToAddress(exe_ctx, name.c_str(), LLDB_INVALID_ADDRESS, &error);
+        addr = ToAddress(exe_ctx, name, LLDB_INVALID_ADDRESS, &error);
         if (addr != LLDB_INVALID_ADDRESS) {
           if (sign[0] == '+')
             return addr + offset;