Trouble with compile of 6.4 under UW7

Sorry, if I am posting to the wrong group.

I am using Unixware 7 and tring to compile postgresql 6.4

I am getting this error:
gmake[2]: Entering directory `/usr/src/pgsql/src/interfaces/libpq++'
c++  -I../../backend -I../../include -I../../interfaces/libpq -I../../include -I
../../backend   -O -K i486,host,inline,loop_unroll,alloca -Dsvr4  -K PIC   -c pg
env.cc -o pgenv.o 
c++: cannot specify -o with -c and multiple compilations

then it stops.

Thanks for all the help.