[gegl] configure: default CFLAGS to -Ofast

[Øyvind Kolås <ok src gnome org>]

commit d11becf349658ea6bd50ac9e8f6f3bc6bde91a64
Author: Øyvind Kolås <pippin gimp org>
Date:   Tue May 15 21:45:31 2018 +0200

    configure: default CFLAGS to -Ofast

 configure.ac |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 379a632..fdd7f64 100644
--- a/configure.ac
+++ b/configure.ac
@@ -191,7 +191,7 @@ AC_PROG_MAKE_SET
 case "$CC" in
   clang* | gcc*)
     if test -z $user_set_cflags; then
-      CFLAGS="-g -O3"
+      CFLAGS="-g -Ofast"
     fi
     ;;
   *)
@@ -201,7 +201,7 @@ esac
 case "$CXX" in
   clang* | g++*)
     if test -z $user_set_cxxflags; then
-      CXXFLAGS="-g -O3"
+      CXXFLAGS="-g -Ofast"
     fi
     ;;
   *)