buildgcc: Add missing '\'

That caused the CFLAGS, CXXFLAGS, and '|| touch .failed' to not be taken
into account when building binutils.

Change-Id: I94521eb73cefdc5ed01fbf10122966a54cc28166
Signed-off-by: Vivia Nikolaidou <vivia.nikolaidou@puri.sm>
Reviewed-on: https://review.coreboot.org/25901
Reviewed-by: Youness Alaoui <snifikino@gmail.com>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/crossgcc/buildgcc

@@ -681,7 +681,7 @@ build_BINUTILS() {
 		--target=${TARGETARCH} --enable-targets=${TARGETARCH}${ADDITIONALTARGET} \
 		--disable-werror --disable-nls --enable-lto --enable-gold \
 		--enable-interwork --enable-multilib \
-		--enable-plugins --enable-multilibs
+		--enable-plugins --enable-multilibs \
 		CFLAGS="$HOSTCFLAGS" \
 		CXXFLAGS="$HOSTCFLAGS" \
 		|| touch .failed