package/systemd: fix build with -Ofast

Update -Ofast workaround as suggested by Yann E. Morin to avoid the
following build failure raised since bump to version 252.4 in commit
a2c823d1f548d5a0120d27d6c000603192360f7b and
https://github.com/systemd/systemd/commit/60f97fee2d2f948c8e8963ea8ff767008cb93cae:

../output-1/build/systemd-252.4/meson.build:397:8: ERROR: Problem encountered: -Ofast, -ffast-math, or -ffinite-math-only is specified in c_args.

Fixes:
 - http://autobuild.buildroot.org/results/8f41c4984b645851724e554c3162b83bc312bee7

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/systemd/systemd.mk

@@ -100,7 +100,7 @@ SYSTEMD_CONF_OPTS += \
 
 SYSTEMD_CFLAGS = $(TARGET_CFLAGS)
 ifeq ($(BR2_OPTIMIZE_FAST),y)
-SYSTEMD_CFLAGS += -O3
+SYSTEMD_CFLAGS += -O3 -fno-finite-math-only
 endif
 
 ifeq ($(BR2_nios2),y)