Build problem with cygwin/mingw

Following steps were followed:

./configure --host=mingw32 --prefix==/cygdrive/c/source/vc/mixer/libmad

Configure step goes fine. The prefix is the dir I want to install to e.g. 
c:\source\vc\mixer\libmad which already exists.

make also works fine

make install goes like this:

--------------------------------------------------------------------------------
$ make install
make  install-recursive
make[1]: Entering directory 
`/cygdrive/c/source/vc/mixer/libmad-0.15.0b/libmad-0
.15.0b'
make[2]: Entering directory 
`/cygdrive/c/source/vc/mixer/libmad-0.15.0b/libmad-0
.15.0b'
make[3]: Entering directory 
`/cygdrive/c/source/vc/mixer/libmad-0.15.0b/libmad-0
.15.0b'
/bin/bash ./mkinstalldirs /cygdrive/c/source/vc/mixer/libmad/lib
  /bin/bash ./libtool --mode=install /usr/bin/install -c  libmad.la 
/cygdrive/c/s
ource/vc/mixer/libmad/lib/libmad.la
/usr/bin/install -c .libs/libmad.lai 
/cygdrive/c/source/vc/mixer/libmad/lib/libm
ad.la
/usr/bin/install -c .libs/libmad.a 
/cygdrive/c/source/vc/mixer/libmad/lib/libmad
.a
ranlib /cygdrive/c/source/vc/mixer/libmad/lib/libmad.a
c:\mingw\bin\ranlib.exe: /cygdrive/c/source/vc/mixer/libmad/lib/libmad.a: 
No suc
h file or directory
make[3]: *** [install-libLTLIBRARIES] Error 9
make[3]: Leaving directory 
`/cygdrive/c/source/vc/mixer/libmad-0.15.0b/libmad-0.
15.0b'
make[2]: *** [install-am] Error 2
make[2]: Leaving directory 
`/cygdrive/c/source/vc/mixer/libmad-0.15.0b/libmad-0.
15.0b'
make[1]: *** [install-recursive] Error 1
make[1]: Leaving directory 
`/cygdrive/c/source/vc/mixer/libmad-0.15.0b/libmad-0.
15.0b'
make: *** [install] Error 2
--------------------------------------------------------------------------------

It looks like ranlib is being passed the cygwin version of the path but it 
doesn't recognize it as it's part of mingw and only allows normal Windows 
paths. What shall I do about this?