Fix error propagation in parseSPIRV (#3362)

d54f77c5 ("[NFC] Split of SPT and SPIR-V in header parsing (#2316)",
2024-03-11) made a copy of the error log, with the presumably unintended
consequence that errors are no longer propagated back to the SPIRVModule
itself.

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@3d58c69cf2f3704

Author: svenvh

llvm-spirv/lib/SPIRV/libSPIRV/SPIRVModule.cpp

@@ -2588,7 +2588,7 @@ std::istream &SPIRVModuleImpl::parseSPIRV(std::istream &I) {
   SPIRVWord Header[5] = {0};
   I.read(reinterpret_cast<char *>(&Header), sizeof(Header));
 
-  SPIRVErrorLog ErrorLog = MI.getErrorLog();
+  SPIRVErrorLog &ErrorLog = MI.getErrorLog();
   if (!ErrorLog.checkError(!I.eof(), SPIRVEC_InvalidModule,
                            "input file is empty") ||
       !ErrorLog.checkError(!I.fail(), SPIRVEC_InvalidModule,