Omit src/port/pipe.c on non-Windows platforms. It's useless and draws

complaints about empty object files on some platforms, eg Darwin.

src/port/Makefile

@@ -15,11 +15,11 @@
 #		for use only by the backend binaries
 #
 # LIBOBJS is set by configure (via Makefile.global) to be the list of
-# object files that are conditionally needed depending on platform.
+# object files that are conditionally needed as determined by configure's probing.
 # OBJS adds additional object files that are always compiled.
 #
 # IDENTIFICATION
-#    $PostgreSQL: pgsql/src/port/Makefile,v 1.36 2008/02/18 14:51:48 petere Exp $
+#    $PostgreSQL: pgsql/src/port/Makefile,v 1.37 2008/11/25 18:19:31 tgl Exp $
 #
 #-------------------------------------------------------------------------
 
@@ -30,7 +30,11 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I$(top_builddir)/src/port -DFRONTEND $(CPPFLAGS)
 LIBS += $(PTHREAD_LIBS)
 
-OBJS = $(LIBOBJS) chklocale.o copydir.o dirmod.o exec.o noblock.o path.o pipe.o pgsleep.o pgstrcasecmp.o qsort.o qsort_arg.o sprompt.o thread.o
+OBJS = $(LIBOBJS) chklocale.o copydir.o dirmod.o exec.o noblock.o path.o \
+	pgsleep.o pgstrcasecmp.o qsort.o qsort_arg.o sprompt.o thread.o
+ifneq (,$(filter $(PORTNAME),cygwin win32))
+OBJS += pipe.o
+endif
 
 # foo_srv.o and foo.o are both built from foo.c, but only foo.o has -DFRONTEND
 OBJS_SRV = $(OBJS:%.o=%_srv.o)