The following bug has been logged on the website:
Bug reference: 14217
Logged by: Dilian Palauzov
Email address: dpa-postgres(at)aegee(dot)org
PostgreSQL version: 9.6beta2
Operating system: Linux
Description:
configure generated by Autoconf loads the file $prefix/etc/config.site and
if CFLAGS is defined there, its value is used when building the project.
Because in postgresql configure.in contains on line 400 "unset CFLAGS" the
value of $CFLAGS from config.site is discarded when building postgresql,
contrary to $LDFLAGS from config.site.
Please remove the "unset CFLAGS" from configure.in and consider replacing
CFLAGS="-v" in src/templates/linux with CFLAGS="$CFLAGS -v".