fix #13633 fix koch boot crashing regression

[timotheecour]

#13606 used the same refactoring pattern in 2 places, it turns out one introduced a regression, and one introduced by accident a bugifx to HCR IIUC:

accidental regression

fixed by this PR:

• fixes koch boot fails if even an empty config.nims is present in ~/.config/nims/ [devel regression] #13633

accidental bugfix

• by accident fixed a bug that's been there probably forever

var currIdx = 0	
  for it in list:	
    # call the C compiler for the .c file:	
    if it.flags.contains(CfileFlag.Cached): continue	
    var compileCmd = getCompileCFileCmd(conf, it, currIdx == list.len - 1, produceOutput=true)

=> 

for idx, it in conf.toCompile:
    # call the C compiler for the .c file:
    if CfileFlag.Cached in it.flags: continue
    let compileCmd = getCompileCFileCmd(conf, it, idx == conf.toCompile.len - 1, produceOutput=true)

so before #13606, when at least one file was cached (if it.flags.contains(CfileFlag.Cached): continue ), currIdx == list.len - 1 would be always false, so isMainFile would be false even for the main module in getCompileCFileCmd, wrongly adding -fpic for the main module:

  if (optGenDynLib in conf.globalOptions or (conf.hcrOn and not isMainFile)) and
      ospNeedsPIC in platform.OS[conf.target.targetOS].props:
    options.add(' ' & CC[c].pic)

[Clyybber]

by accident fixed a bug that's been there probably forever

That wasn't by accident :)

Seems like I was a tad bit quicker here :p

[timotheecour]

That wasn't by accident :)

but I didn't see it mentioned in your PR, this should definitely be mentioned ; maybe add it to your merged PR that this fixes XYZ, maybe some old obscure HCR bug got unfixed, who knows

[Clyybber]

Yeah, it fixes a HCR bug. (at least thats where I saw it surface once)

[timotheecour]

also, this PR that you closed was fixing another bug, but I dont' have rights to re-open my own PR so I'll open a new one...

[Clyybber]

Oh, sorry. I can reopen if you want to? Its the \n typo right?

[timotheecour]

ya; I've now rebased...