Prevent accidental linking of system-supplied copies of libpq.so etc.

Back-patch commit dddfc4cb2, which broke LDFLAGS and related Makefile
variables into two parts, one for within-build-tree library references and
one for external libraries, to ensure that the order of -L flags has all
of the former before all of the latter.  This turns out to fix a problem
recently noted on buildfarm member peripatus, that we attempted to
incorporate code from libpgport.a into a shared library.  That will fail on
platforms that are sticky about putting non-PIC code into shared libraries.
(It's quite surprising we hadn't seen such failures before, since the code
in question has been like that for a long time.)

I think that peripatus' problem could have been fixed with just a subset
of this patch; but since the previous issue of accidentally linking to the
wrong copy of a Postgres shlib seems likely to bite people in the field,
let's just back-patch the whole change.  Now that commit dddfc4cb2 has
survived some beta testing, I'm less afraid to back-patch it than I was
at the time.

This also fixes undesired inclusion of "-DFRONTEND" in pg_config's CPPFLAGS
output (in 9.6 and up) and undesired inclusion of "-L../../src/common" in
its LDFLAGS output (in all supported branches).

Back-patch to v10 and older branches; this is already in v11.

Discussion: https://postgr.es/m/20180704234304.bq2dxispefl65odz@ler-imac.local

6 files changed, 6 insertions, 7 deletions

diff --git a/contrib/dblink/Makefile b/contrib/dblink/Makefile
index e833b9203ac..a5b59c6b41f 100644
--- a/contrib/dblink/Makefile
+++ b/contrib/dblink/Makefile
@@ -3,7 +3,7 @@
 MODULE_big = dblink
 OBJS	= dblink.o
 PG_CPPFLAGS = -I$(libpq_srcdir)
-SHLIB_LINK = $(libpq)
+SHLIB_LINK_INTERNAL = $(libpq)
 
 EXTENSION = dblink
 DATA = dblink--1.1.sql dblink--1.0--1.1.sql dblink--unpackaged--1.0.sql
diff --git a/contrib/oid2name/Makefile b/contrib/oid2name/Makefile
index f695b4a84e1..b41f8af6661 100644
--- a/contrib/oid2name/Makefile
+++ b/contrib/oid2name/Makefile
@@ -7,7 +7,7 @@ PROGRAM = oid2name
 OBJS	= oid2name.o
 
 PG_CPPFLAGS = -I$(libpq_srcdir)
-PG_LIBS = $(libpq_pgport)
+PG_LIBS_INTERNAL = $(libpq_pgport)
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
diff --git a/contrib/pgbench/Makefile b/contrib/pgbench/Makefile
index b8f5fb467f6..d6fbdcc0d69 100644
--- a/contrib/pgbench/Makefile
+++ b/contrib/pgbench/Makefile
@@ -7,7 +7,8 @@ PROGRAM = pgbench
 OBJS	= pgbench.o
 
 PG_CPPFLAGS = -I$(libpq_srcdir)
-PG_LIBS = $(libpq_pgport) $(PTHREAD_LIBS)
+PG_LIBS_INTERNAL = $(libpq_pgport)
+PG_LIBS = $(PTHREAD_LIBS)
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
diff --git a/contrib/postgres_fdw/Makefile b/contrib/postgres_fdw/Makefile
index c0f4160f6ba..bfb2e1d7681 100644
--- a/contrib/postgres_fdw/Makefile
+++ b/contrib/postgres_fdw/Makefile
@@ -4,7 +4,7 @@ MODULE_big = postgres_fdw
 OBJS = postgres_fdw.o option.o deparse.o connection.o
 
 PG_CPPFLAGS = -I$(libpq_srcdir)
-SHLIB_LINK = $(libpq)
+SHLIB_LINK_INTERNAL = $(libpq)
 
 EXTENSION = postgres_fdw
 DATA = postgres_fdw--1.0.sql
diff --git a/contrib/spi/Makefile b/contrib/spi/Makefile
index 0c11bfcbbd4..f6ffe71c020 100644
--- a/contrib/spi/Makefile
+++ b/contrib/spi/Makefile
@@ -16,8 +16,6 @@ DOCS = $(addsuffix .example, $(MODULES))
 # comment out if you want a quieter refint package for other uses
 PG_CPPFLAGS = -DREFINT_VERBOSE
 
-LDFLAGS_SL += -L$(top_builddir)/src/port -lpgport
-
 ifdef USE_PGXS
 PG_CONFIG = pg_config
 PGXS := $(shell $(PG_CONFIG) --pgxs)
diff --git a/contrib/vacuumlo/Makefile b/contrib/vacuumlo/Makefile
index b658f9bf6f8..ccb7d074085 100644
--- a/contrib/vacuumlo/Makefile
+++ b/contrib/vacuumlo/Makefile
@@ -7,7 +7,7 @@ PROGRAM = vacuumlo
 OBJS	= vacuumlo.o
 
 PG_CPPFLAGS = -I$(libpq_srcdir)
-PG_LIBS = $(libpq_pgport)
+PG_LIBS_INTERNAL = $(libpq_pgport)
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config