Codechange: [MinGW] use pe-bigobj-x86-64 format for x64 debug builds

[glx22]

Motivation / Problem

When trying to understand why #10001 compilation was failing for MinGW x64 debug builds, I compared objdump -t network_command.cpp.obj from master and #10001.

objdump -t snippet for #10001
[85159](sec -32108)(fl 0x00)(ty    0)(scl   2) (nx 0) 0x0000000000000000 .refptr._Z19CmdClearOrderBackup13DoCommandFlag9TileIndex8ClientID
objdump -t snippet for master
[80970](sec 31671)(fl 0x00)(ty    0)(scl   2) (nx 0) 0x0000000000000000 .refptr._Z19CmdClearOrderBackup13DoCommandFlag9TileIndex8ClientID

I noticed a lot of negative section values in #10001, so I though maybe we have too many sections (even if the compiler doesn't complain about that). I then tried to enable pe-bigobj-x86-64 and that solved the issue for #10001.

Then I decided to test something and commented out the ASLR disabling, and #10001 still build fine.
So I tried the same on master, and it builds too.

So in the end it seems OpenTTD again managed to hit some compiler limits (remember the settings hell on macos).

Description

Add -Wa,-mbig-obj compile flag for MinGW x64 debug builds.
As a side effect, ASLR disabling in link options is not needed anymore, and removed.

Limitations

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker

[TrueBrain]

I don't even ... how do you figure out these things?