Make Problems

When i try to compile postgres 8 on windows machine i get this error
after i issue the make command

make -C doc all
make[1]: Entering directory `/src/pgsql/doc'
make[1]: Nothing to be done for `all'.
make[1]: Leaving directory `/src/pgsql/doc'
make -C src all
make[1]: Entering directory `/src/pgsql/src'
make -C port all
make[2]: Entering directory `/src/pgsql/src/port'
gcc -O2 -Wall -Wmissing-prototypes -Wpointer-arith -fno-strict-aliasing
-I../../src/port -DFRONTEND -I../../src/include
-I./src/include/port/win32 -DEXEC_BACKEND
"-I../../src/include/port/win32" -c -o open.o open.c
open.c: In function `win32_open':
open.c:67: `O_SEQUENTIAL' undeclared (first use in this function)
open.c:67: (Each undeclared identifier is reported only once
open.c:67: for each function it appears in.)
make[2]: *** [open.o] Error 1
make[2]: Leaving directory `/src/pgsql/src/port'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/src/pgsql/src'
make: *** [all] Error 2