Makefile: move some flags to examples makefiles

This commit moves some flags which are used
under examples/ directory only.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/examples/standalone/Makefile b/examples/standalone/Makefile
index cad4409..1f8d70c 100644
--- a/examples/standalone/Makefile
+++ b/examples/standalone/Makefile
@@ -5,6 +5,10 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
+ifdef FTRACE
+CFLAGS += -finstrument-functions -DFTRACE
+endif
+
 extra-y        := hello_world
 extra-$(CONFIG_SMC91111)           += smc91111_eeprom
 extra-$(CONFIG_SMC911X)            += smc911x_eeprom