Provide and use a makefile target to build all generated headers.

As of 9.6, pg_regress doesn't build unless storage/lwlocknames.h has been
created; but there was nothing forcing that to happen if you just went into
src/test/regress/ and built there.  We previously had a similar complaint
about plpython.

To fix in a way that won't break next time we invent a generated header,
make src/backend/Makefile expose a phony target for updating all the
include files it builds, and invoke that before building pg_regress or
plpython.  In principle, maybe we ought to invoke that everywhere; but
it would add a lot of usually-useless make cycles, so let's just do it
in the places where people have complained.

I made a couple of cosmetic adjustments in src/backend/Makefile as well,
to deal with the generated headers in consistent orders.

Michael Paquier and Tom Lane

Report: <31398.1467036827@sss.pgh.pa.us>
Report: <20150916200959.GB32090@msg.df7cb.de>

src/pl/plpython/Makefile

@@ -95,7 +95,7 @@ REGRESS_PLPYTHON3_MANGLE := $(REGRESS)
 
 include $(top_srcdir)/src/Makefile.shlib
 
-all: all-lib
+all: submake-generated-headers all-lib
 
 
 install: all install-lib install-data
@@ -119,15 +119,15 @@ uninstall-data:
 include $(srcdir)/regress-python3-mangle.mk
 
 
-check: submake
+check: submake-pg-regress
 	$(pg_regress_check) $(REGRESS_OPTS) $(REGRESS)
 
-installcheck: submake
+installcheck: submake-pg-regress
 	$(pg_regress_installcheck) $(REGRESS_OPTS) $(REGRESS)
 
 
-.PHONY: submake
-submake:
+.PHONY: submake-pg-regress
+submake-pg-regress:
 	$(MAKE) -C $(top_builddir)/src/test/regress pg_regress$(X)
 
 clean distclean: clean-lib