Fixed compilation on Haiku

[Teashrock]

Fixed #13017.
It's a temporary solution, I suppose.

[Araq]

Such a weird bug, maybe instead compile koch.nim with --gc:none (it doesn't allocate all that much memory anyway),

[Teashrock]

@Araq
I'll try this. Meanwile, I decided to open Python console and apply ord() to both of characters. ':' is 58, and '/' is 47. This is a difference by 11. Maybe there's some bitwise operation accidently doing this?

[Araq]

Who knows but it doesn't seem likely.

[Teashrock]

@Araq
Now it tries to lauch ./koch boot -d:release automatically right after it's compilation and then throws said error.

And no, manually compiling koch with --gc:none didn't help. Still the same error.

[Araq]

Well sorry, this workaround is unacceptable. We need to find and fix the root cause.

[Teashrock]

@Araq
Actually, it may even be a bug in Haiku's GCC 8, not in compiler sources.

[Teashrock]

But no, then it would be GCC complaining... So, it's not the case.

[Araq]

Huh? Of course GCC could produce wrong code and then we would see this behavior.

[Teashrock]

@Araq
My bad. I just was too sleepy at that moment. I'll check.

[Teashrock]

@Araq
I sorta localized the bug. With 90% probability it's at os.'/' It's a simple "joinPath" function. This function for some unknown reason converts any group of ':' to '/' or nothing. In fact, just perceives it like path divider.

Examples:
1:

echo "one:two:three"

Result: one:two:three

2:

import os

echo "one:two" / ":three"
echo "test::::::::" / "test"
echo "test" / "::::::::test"
echo "test::::" / "::::test"

Result:
one/two/three
test/test
test/test
test/test

[Araq]

osseps.nim contains this section

  AltSep* =
    when doslikeFileSystem: '/'
    elif defined(haiku): ':'
    else: DirSep

which seems to be responsible. :-)

[genotrance]

elif defined(haiku): ':'

This was inherited from platform.nim and wasn't in the original osseps.nim prior to this PR.

[Teashrock]

@Araq
What the heck? O_O What sort of "genius" did this? I thought this was a bug, and this happened to be intended!

Give me time, I'll make another pull request.