[JITLink] Use rsplit on -sectcreate argument in llvm-jitlink (#115511)

This accounts for cases where the file path may contain an `@` symbol.
In such cases, the split occurs too early causing argument parsing to
fail.

Author: dgg5503

llvm/test/ExecutionEngine/JITLink/Generic/Inputs/sectcreate-data.txt renamed to llvm/test/ExecutionEngine/JITLink/Generic/Inputs/sect@create/sectcreate-data.txt

@@ -1,6 +1,6 @@
 # RUN: llc -filetype=obj -o %t.o %S/Inputs/main-ret-0.ll
 # RUN: llvm-jitlink -noexec \
-# RUN:   -sectcreate __data,%S/Inputs/sectcreate-data.txt@foo=0 \
+# RUN:   -sectcreate __data,%S/Inputs/sect@create/sectcreate-data.txt@foo=0 \
 # RUN:   %t.o
 #
 # Use -sectcreate to create a section from a data file.

llvm/test/ExecutionEngine/JITLink/Generic/sectcreate.test

@@ -1740,7 +1740,7 @@ static Error addSectCreates(Session &S,
 
     StringRef SCArg(*SCItr);
 
-    auto [SectAndFileName, ExtraSymbolsString] = SCArg.split('@');
+    auto [SectAndFileName, ExtraSymbolsString] = SCArg.rsplit('@');
     auto [SectName, FileName] = SectAndFileName.rsplit(',');
     if (SectName.empty())
       return make_error<StringError>("In -sectcreate=" + SCArg +