toolchain: remove gcc libssp and use libc variant

Removes the standalone implementation of stack smashing protection
in gcc's libssp in favour of the native implementation available
in glibc and uclibc. Musl libc already uses its native ssp, so this
patch does not affect musl-based toolchains.

Stack smashing protection configuration options are now uniform
across all supported libc variants.

This also makes kernel-level stack smashing protection available
for x86_64 and i386 builds using non-musl libc.

Signed-off-by: Ian Cooper <iancooper@hotmail.com>

toolchain/glibc/common.mk

@@ -39,7 +39,6 @@ ifeq ($(ARCH),mips64)
   endif
 endif
 
-
 # -Os miscompiles w. 2.24 gcc5/gcc6
 # only -O2 tested by upstream changeset
 # "Optimize i386 syscall inlining for GCC 5"
@@ -61,6 +60,8 @@ GLIBC_CONFIGURE:= \
 		--without-cvs \
 		--enable-add-ons \
 		--$(if $(CONFIG_SOFT_FLOAT),without,with)-fp \
+		  $(if $(CONFIG_PKG_CC_STACKPROTECTOR_REGULAR),--enable-stack-protector=yes) \
+		  $(if $(CONFIG_PKG_CC_STACKPROTECTOR_STRONG),--enable-stack-protector=strong) \
 		--enable-kernel=4.14.0
 
 export libc_cv_ssp=no