Fix issue 22863 - -main doesn't work anymore when used for linking only

[dkorpel]

Porting ldc-developers/ldc#3938 to DMD

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22863	regression	[REG2.099] -main doesn't work anymore when used for linking only (without source modules)

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "stable + dmd#13830"

[kinke]

Inserting at position 0 is just an LDC specificum for -singleobj, DMD shouldn't need it and probably just append it, as for the !oneobj case.

[ljmf00]

There are some .debug_ranges conflicts on debug info for -main generated functions. Perhaps, is this somewhat related?

[dkorpel]

circleci:

ERROR: Found the following residual temporary files.
ERROR: Temporary files should be stored in `test_results` or explicitly removed.
?? test/foo

Not sure why it's not deleted, dmd gets passed -od=${OUTPUT_BASE} and rm_retry -r ${OUTPUT_BASE} follows.

[kinke]

-od just specifies the object files dir IIRC, doesn't affect the executable output dir.

[WalterBright]

I'll defer to @kinke on this one. -Walter