postgresql: work around occasional build failures due to a dependency race

There are two routes to building jsonapi.o, and one of them adds CPPFLAGS
that then break the build.  Ensure the correct route is always taken by
explicitly building it first.

This has been reported upstream and more details are in the linked mail.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>

meta-oe/recipes-dbs/postgresql/postgresql.inc

@@ -181,6 +181,13 @@ do_configure() {
     fi
 }
 
+# There's a makefile dependency race that causes occasional build
+# failures, so build this object first to avoid the race.
+# https://www.postgresql.org/message-id/CAAnfSTv_Vj9oH2vUs56KwDdbmfrOhuTb1o%2B6TXzBW_uUjOJpkg%40mail.gmail.com
+do_compile:prepend() {
+    make -C src/common jsonapi.o
+}
+
 do_compile:append() {
     oe_runmake -C contrib all