Added test for -elf configuration, to see that _alloca call is properly 
generated. See:

http://llvm.org/viewvc/llvm-project?view=revision&revision=193289



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193321 91177308-0d34-0410-b5e6-96231b3b80d8