Do not include installer dir when looking for distfiles

[liback]

When installing nQuake the user is asked to decide where to install distfiles. However, the installer will also look for distfiles in the same directory as the installer .exe file. This is not intuitive and may cause problems if running the nQuake installer from the browser downloads folder that may at the same time contain old version of distribution files (especially for people maintaining nQuake).

See

client-win32/src/nquake-installer_source.nsi

Line 1088 in aea2e9a

${If} ${FileExists} "$EXEDIR\$R0"

Function .installSection
  Pop $R1 # distfile info
  Pop $R0 # distfile filename
  Call .checkDistfileDate
  ${If} ${FileExists} "$EXEDIR\$R0"
    DetailPrint "Extracting $R1, please wait..."
    nsisunz::UnzipToStack "$EXEDIR\$R0" $INSTDIR
  ${ElseIf} ${FileExists} "$DISTFILES_PATH\$R0"
[.......omitted for brevity]