Unbreak the gcc build (workaround a gcc bug)

[davide]

Summary

[2571/2602] Building CXX object tools/llvm-extract/CMakeFiles/llvm-extract.dir/llvm-extract.cpp.o
../tools/llvm-extract/llvm-extract.cpp: In function ‘int main(int, char**)’:
../tools/llvm-extract/llvm-extract.cpp:226:44: warning: ISO C++ forbids zero-size array ‘argv’ [-Wpedantic]

ExitOnError ExitOnErr(std::string(argv[0]) + ": error reading input: ");
                                         ^

Sorry for the lack of context. GCC reference bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61259

[pcc]

LGTM

tools/lli/lli.cpp

 
   // If not jitting lazily, load the whole bitcode file eagerly too.
   if (NoLazyCompilation) {
-    ExitOnError ExitOnErr(std::string(argv[0]) +
+    ExitOnError ExitOnErr(std::string(*argv) +
                           ": bitcode didn't read correctly: ");
     ExitOnErr(Mod->materializeAll());
   }

tools/llvm-extract/llvm-extract.cpp

     }
   }
 
-  ExitOnError ExitOnErr(std::string(argv[0]) + ": error reading input: ");
+  ExitOnError ExitOnErr(std::string(*argv) + ": error reading input: ");
 
   auto Materialize = [&](GlobalValue &GV) { ExitOnErr(GV.materialize()); };