Mac OS X: compiling for 10.5 under 10.6

[Soenke Hahn]

Hi!

I was trying to use the ghc on a system with OS X 10.6 to compile for
both 10.6 and 10.5 (and hopefully 10.7). In the past (with ghc-7.2.2
IIRC) I had luck with

if os(darwin)
  cc-options:
    -isysroot /Developer/SDKs/MacOSX10.5.sdk -mmacosx-version-min=10.5
  ld-options:
    -isysroot /Developer/SDKs/MacOSX10.5.sdk -mmacosx-version-min=10.5

in the cabal file, but with ghc-7.4.1 (from Haskell-Platform-2012.2.0.0)
I get linker errors:

Undefined symbols:
  "_fopen$DARWIN_EXTSN", referenced from:
      _procRtsOpts in libHSrts.a(RtsFlags.o)
      _initProfiling2 in libHSrts.a(ProfHeap.o)
      _exitHpc in libHSrts.a(Hpc.o)
      _startupHpc in libHSrts.a(Hpc.o)
  "_fopen$UNIX2003", referenced from:
      _loadArchive in libHSrts.a(Linker.o)
      _addDLL in libHSrts.a(Linker.o)
  "_kevent64", referenced from:
      _s3VN_info in libHSbase-4.5.0.0.a(KQueue__166.o)
ld: symbol(s) not found

If I remove the backward-compatibility flags from the cabal file,
everything works fine. (I assume it won't run on OS X 10.5 then, of course.)

If I understand correctly the RTS and the base library in ghc-7.4.1
depend on a newer version of the OS X SDK (>= 10.6). Is there an easy
way to work around this version constraint? If not, does that mean,
ghc-7.4.1 does not support OS X 10.5?

Thanks,
Sönke