arch/Config.in.x86: westmere and silvermont were added in gcc 4.9

These were added in gcc commit
d3c11974032e21121a051d423a1d71097edf752f ("Use proper Intel processor
names for -march=/-mtune=") which was merged in gcc 4.9.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

arch/Config.in.x86

@@ -196,6 +196,7 @@ config BR2_x86_westmere
 	select BR2_X86_CPU_HAS_SSSE3
 	select BR2_X86_CPU_HAS_SSE4
 	select BR2_X86_CPU_HAS_SSE42
+	select BR2_ARCH_NEEDS_GCC_AT_LEAST_4_9
 config BR2_x86_corei7_avx
 	bool "corei7-avx"
 	select BR2_X86_CPU_HAS_MMX
@@ -273,6 +274,7 @@ config BR2_x86_silvermont
 	select BR2_X86_CPU_HAS_SSSE3
 	select BR2_X86_CPU_HAS_SSE4
 	select BR2_X86_CPU_HAS_SSE42
+	select BR2_ARCH_NEEDS_GCC_AT_LEAST_4_9
 config BR2_x86_k6
 	bool "k6"
 	depends on !BR2_x86_64