toolchain: add gcc configure default PIE and SSP

GCC supports starting version 5 --enable-default-ssp and starting version 6
--enable-default-pie.

It produces hardened binaries by default without dealing with package
compilation flags.

Signed-off-by: Julien Dusser <julien.dusser@free.fr>

toolchain/gcc/Config.in

@@ -37,6 +37,21 @@ config EXTRA_GCC_CONFIG_OPTIONS
 	help
 	    Any additional gcc options you may want to include....
 
+config GCC_DEFAULT_PIE
+	bool
+	prompt "Build executable with PIE enabled by default" if TOOLCHAINOPTS
+	depends on !GCC_USE_VERSION_5
+	default n
+	help
+	    Use gcc configure option --enable-default-pie to turn on -fPIE and -pie by default.
+
+config GCC_DEFAULT_SSP
+	bool
+	prompt "Build executable with Stack-Smashing Protection enabled by default" if TOOLCHAINOPTS
+	default n
+	help
+	    Use gcc configure option --enable-default-ssp to turn on -fstack-protector-strong by default.
+
 config SSP_SUPPORT
 	bool
 	prompt "Enable Stack-Smashing Protection support" if TOOLCHAINOPTS

toolchain/gcc/common.mk

@@ -133,6 +133,16 @@ ifndef GCC_VERSION_4_8
   GCC_CONFIGURE += --with-diagnostics-color=auto-if-env
 endif
 
+ifneq ($(CONFIG_GCC_DEFAULT_PIE),)
+  GCC_CONFIGURE+= \
+		--enable-default-pie
+endif
+
+ifneq ($(CONFIG_GCC_DEFAULT_SSP),)
+  GCC_CONFIGURE+= \
+		--enable-default-ssp
+endif
+
 ifneq ($(CONFIG_SSP_SUPPORT),)
   GCC_CONFIGURE+= \
 		--enable-libssp