Build applications linking libpq with -pthread on openbsd

OpenBSD require that linking with a library using sigwait(3) be
compiled with -pthread.  This adds a kludge in the relevant
makefiles which is less than elegant, but it seemed the least
intrusive change to make.

src/bin/pg_ctl/Makefile

@@ -25,6 +25,10 @@ LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses -lcurl -lssl
 
 override CPPFLAGS := -DDEF_PGPORT=$(DEF_PGPORT) -I$(libpq_srcdir) $(CPPFLAGS)
 
+ifeq ($(PORTNAME),openbsd)
+override CFLAGS += -pthread
+endif
+
 OBJS=	pg_ctl.o $(WIN32RES)
 
 all: pg_ctl

src/bin/pg_dump/Makefile

@@ -25,6 +25,10 @@ LIBS := $(filter-out -lreadline -ledit -ltermcap -lncurses -lcurses -lcurl , $(L
 # the use of tempnam in pg_backup_tar.c causes a warning when using newer versions of GCC
 override CPPFLAGS := -Wno-deprecated-declarations -I$(libpq_srcdir) $(CPPFLAGS)
 
+ifeq ($(PORTNAME),openbsd)
+override CFLAGS += -pthread
+endif
+
 OBJS=	pg_backup_archiver.o pg_backup_db.o pg_backup_custom.o \
 	pg_backup_files.o pg_backup_null.o pg_backup_tar.o \
 	pg_backup_directory.o dumputils.o compress_io.o $(WIN32RES)

src/bin/scripts/Makefile

@@ -26,8 +26,13 @@ PROGRAMS = createdb createlang createuser dropdb droplang dropuser clusterdb vac
 
 override CPPFLAGS := -I$(top_srcdir)/src/bin/pg_dump -I$(top_srcdir)/src/bin/psql -I$(libpq_srcdir) $(CPPFLAGS)
 
+
 all: $(PROGRAMS)
 
+ifeq ($(PORTNAME),openbsd)
+override CFLAGS += -pthread
+endif
+
 %: %.o $(WIN32RES)
 	$(CC) $(CFLAGS) $^ $(libpq_pgport) $(LDFLAGS) $(LDFLAGS_EX) $(LIBS) -o $@$(X)