A double pointer was being passed to the call to FortranStart rather than just a pointer to the EnvironmentDefaults.list. This now passes `null` directly when there's no EnvironmentDefaults.list and passes the list directly when there is, removing the original global variable which was a pointer to a pointer containing null or the EnvironmentDefaults.list global.
Fixes#90537
This patch changes the behaviour for flang to only create and link to a
`main` entry point when the Fortran code has a program statement in it.
This means that flang-new can be used to link even when the program is
a mixed C/Fortran code with `main` present in C and no entry point
present in Fortran.
This also removes the `-fno-fortran-main` flag as this no longer has any
functionality.
