when creating an executable, always set global.params.objname = NULL

In that case, -of is just not supposed to name the object file.
This makes ldmd2 work with rdmd.
Merge pull request #283 from klickverbot/master

Cleanup.
Added back NULL returns accidentally removed in 8ff3a8060.

No functionality change, as the return value wasn't used
anywhere.
Some more assert(false) -> llvm_unreachable.
Proper merge of ldc-merge-2.061 druntime branch into main ldc branch.
Merge remote-tracking branch 'NilsBossung/master'
Folded in callWithStackShell() fix.
Revert "Revert "Fix overly conservative inlining prediction".",

The previous failures were caused by the issue in
callWithStackShell(), which is fixed now.

This reverts commit 4a6444c3207c01238484785dbbca44257fde6370.