Run:

export PATH=/c/_32/Python27:/c/GTK+3.6.1/bin:.:/usr/local/bin:/mingw/bin:/bin
export PKG_CONFIG_PATH=/c/GTK+3.6.1/lib/pkgconfig
export GOBJECT_CFLAGS=-IC:/Gtk+3.6.1/include
export GOBJECT_LIBS=-LC:/Gtk+3.6.1/lib
export GMODULE_CFLAGS=-IC:/Gtk+3.6.1/include
export GMODULE_LIBS=-LC:/Gtk+3.6.1/lib
export GLIB_CFLAGS=-IC:/Gtk+3.6.1/include
export GLIB_LIBS=-LC:/Gtk+3.6.1/lib
export GIO_LIBS=-LC:/Gtk+3.6.1/lib
export GIO_CFLAGS=-IC:/Gtk+3.6.1/include

In configure script, change:
	PYTHON_LIBS="-L${py_prefix}/lib -lpython${PYTHON_VERSION}"
to:
	PYTHON_LIBS="-L${py_prefix}/lib -lpython"

Run the following configure command:
./configure --prefix=/c/Gtk+3.6.1 --disable-static --enable-shared LDFLAGS="-L/c/Gtk+3.6.1/lib -L/c/Python27/Lib -L/c/_32/Python27/Lib/site-packages -L/c/_32/Python27/libs" CPPFLAGS="-I/c/Gtk+3.6.1/include -I/c/GTK+3.6.1/lib/glib-2.0/include -I/c/Gtk+3.6.1/include/glib-2.0 -I/c/_32/Python27/include" LIBS="-lgobject-2.0.dll -lgio-2.0.dll -lglib-2.0.dll" 

Then, in all of the generated Makefiles:

Makefile
m4/Makefile
tests/Makefile
tests/offsets/Makefile
tests/scanner/Makefile
tests/repository/Makefile
tests/warn/Makefile
tests/doctool/Makefile
docs/Makefile
docs/reference/Makefile

run the script at the bottom of this page in order to change:

PYTHON_INCLUDES = -IC:\_32\Python27/include/python2.7
PYTHON_LIBS = -LC:\_32\Python27/lib -lpython
PYTHON_LIB_LOC = C:\_32\Python27/lib

to:

PYTHON_INCLUDES = -I/c/_32/Python27/include/python2.7
PYTHON_LIBS = -L/c/_32/Python27/lib -lpython
PYTHON_LIB_LOC = /c/_32/Python27/lib

Turn on verbosity for 'make' by running 'make V=1'.

Before running make, modify giscanner/giscannermodule.c to load msvcr90.dll instead of
msvcr71.dll. (Earlier python binaries use msvcr71.dll, but my 2.7 uses msvcr90.dll.) 

That gets us to:
IOError: [Errno 2] No such file or directory: '.\\.libs\\.libs\\_giscanner.pyd'

'cd' to .libs folder, run 'mkdir .libs', 'cd ..'.
Copy .libs/_giscanner.pyd to .libs/.libs/_giscanner.pyd and re-run 'make V=1'.

Results in:
WindowsError: [Error 193] %1 is not a valid Win32 application



__END__


use strict;
use warnings;

my @make = qw(
 Makefile
 m4/Makefile
 tests/Makefile
 tests/offsets/Makefile
 tests/scanner/Makefile
 tests/repository/Makefile
 tests/warn/Makefile
 tests/doctool/Makefile
 docs/Makefile
 docs/reference/Makefile
);

for my $mf(@make) {
  print "Amending $mf\n";
  open RD, '<', $mf or die "Can't open $mf for reading: $!";
  open WR, '>', "${mf}_new" or die "Can't open ${mf}_new for writing: $!";

  while(<RD>) {
    $_ =~ s/PYTHON_INCLUDES = \-Ic:\\_32\\Python27\/include\/python2\.7/PYTHON_INCLUDES = \-I\/c\/_32\/Python27\/include\/python2\.7/;
    $_ =~ s/PYTHON_LIBS = \-Lc:\\_32\\Python27\/lib \-lpython/PYTHON_LIBS = \-L\/c\/_32\/Python27\/lib \-lpython/;
    $_ =~ s/PYTHON_LIB_LOC = c:\\_32\\Python27\/lib/PYTHON_LIB_LOC = \/c\/_32\/Python27\/lib/;
    $_ =~ s/C:\//\/c\//gi;
    print WR $_;
  }
  close RD or die "Couldn't close $mf after reading: $!";
  close WR or die "Couldn't close ${mf}_new after writing: $!";

  die "Couldn't rename $mf to ${mf}_orig"
    unless rename $mf, "${mf}_orig";

  die "Couldn't rename ${mf}_new to $mf"
    unless rename "${mf}_new", $mf;
}