Fix pg_rewind link order issue introduced in 927474ce.

The aforementioned commit orders the link to pgfeutils after libpq,
which can fail because pgfeutils uses symbols from libpq.

Per buildfarm animal jacana.

Author: Andres Freund
Discussion: https://postgr.es/m/20190930192013.r3wievljua2n3tbb@alap3.anarazel.de

src/bin/pg_rewind/Makefile

@@ -16,7 +16,7 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 override CPPFLAGS := -I$(libpq_srcdir) -DFRONTEND $(CPPFLAGS)
-LDFLAGS_INTERNAL += $(libpq_pgport) -L$(top_builddir)/src/fe_utils -lpgfeutils
+LDFLAGS_INTERNAL += -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport)
 
 OBJS	= pg_rewind.o parsexlog.o xlogreader.o datapagemap.o timeline.o \
 	fetch.o file_ops.o copy_fetch.o libpq_fetch.o filemap.o \