[PATCH v2] configure: Fix default -O2 being added when CFLAGS not set

[Glenn Washburn <development@efficientek.com>]

Autoconf will set a default CFLAGS of "-g -O2" if CFLAGS is not set. CFLAGS
was defaulted to "" early in configure to prevent this. A recent commit
ad9ccf660013c208077b1e983d6c824df25ed1cf ("configure: Fix various new
autotools warnings") added AC_USE_SYSTEM_EXTENSIONS, which pulls in the
autoconf CFLAGS check, before we default CFLAGS and thus setting the
autoconf default for CFLAGS. Move the default setting of CFLAGS to before
AC_USE_SYSTEM_EXTENSIONS so that autoconf will see CFLAGS as set and not
give it a default.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Robbie Harwood <rharwood@redhat.com>
Tested-by: Paul Menzel <pmenzel@molgen.mpg.de>
---
 configure.ac | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index 3ffbc7c57b..c1e50c9d75 100644
--- a/configure.ac
+++ b/configure.ac
@@ -36,12 +36,12 @@ dnl description of the relationships between them.
 
 AC_INIT([GRUB],[2.11],[bug-grub@gnu.org])
 
-AC_USE_SYSTEM_EXTENSIONS
-AC_CONFIG_AUX_DIR([build-aux])
-
 # We don't want -g -O2 by default in CFLAGS
 : ${CFLAGS=""}
 
+AC_USE_SYSTEM_EXTENSIONS
+AC_CONFIG_AUX_DIR([build-aux])
+
 # Checks for build, host and target systems.
 AC_CANONICAL_BUILD
 AC_CANONICAL_HOST
-- 
2.27.0