i386: properly define BR2_ARCH for all x86 subarchitectures

We were not defining BR2_ARCH for two of the x86 subarchitecture,
which means the architecture part of the GNU_TARGET_NAME tuple was
empty, leading to weird build failures.

This commit fixes that by defining the appropriate values.

Fixes bug #8861.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

arch/Config.in.x86

@@ -226,6 +226,8 @@ config BR2_ARCH
 	default "i686"		if BR2_x86_nocona && BR2_i386
 	default "i686"		if BR2_x86_core2 && BR2_i386
 	default "i686"		if BR2_x86_corei7 && BR2_i386
+	default "i686"		if BR2_x86_corei7_avx && BR2_i386
+	default "i686"		if BR2_x86_corei7_avx2 && BR2_i386
 	default "i686"		if BR2_x86_atom && BR2_i386
 	default "i686"		if BR2_x86_opteron && BR2_i386
 	default "i686"		if BR2_x86_opteron_sse3 && BR2_i386