[clang] [flang] Revert "[flang][Driver] Let the linker fail on multiple definitions of main()" (PR #74120)

[Michael Klemm via cfe-commits]

mjklemm wrote:

> For what it's worth, `armflang` follows gfortran's behavior.

So does the "old legacy flang", which I guess is the basis for armflang.  AOCC's flang shows the same behavior.


> As there isn't consensus amongst fortran compilers, I'm unsure which behavior we should follow. What do other's think?

I guess, we could agree that the current behavior of flang-new ignoring the Fortran program unit is present, is not correct either. :-)

Could please see if `-Wl,--allow-multiple-definition` would help to resolve the issue in the application?

https://github.com/llvm/llvm-project/pull/74120