configure: Don't disable optimization for non-fortify builds

Commit b553a042 inadvertently disabled optimization
for all non-fortify builds. Fix this bug so we only do an
unoptimized build if we want debug.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 1447082049-25099-1-git-send-email-peter.maydell@linaro.org

configure

@@ -4451,6 +4451,8 @@ if test "$gcov" = "yes" ; then
   LDFLAGS="-fprofile-arcs -ftest-coverage $LDFLAGS"
 elif test "$fortify_source" = "yes" ; then
   CFLAGS="-O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 $CFLAGS"
+elif test "$debug" = "no"; then
+  CFLAGS="-O2 $CFLAGS"
 fi
 
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