build: remove backend build for sapphirerapids

sapphire rapids has amx support but it ends up having a negative
performance impact.

emerald rapids also has amx support with a positive performance impact
however there's no reasonable way in ggml to differentiate between the
two. the impact is small (~6%) so disable amx entirely for simplicity

llama/patches/0018-remove-amx.patch

+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Michael Yang <mxyng@pm.me>
+Date: Tue, 18 Feb 2025 14:47:21 -0800
+Subject: [PATCH] remove amx
+
+---
+ ggml/src/CMakeLists.txt | 4 ----
+ 1 file changed, 4 deletions(-)
+
+diff --git a/ggml/src/CMakeLists.txt b/ggml/src/CMakeLists.txt
+index 72b488dd..50828717 100644
+--- a/ggml/src/CMakeLists.txt
++++ b/ggml/src/CMakeLists.txt
+@@ -293,10 +293,6 @@ if (GGML_CPU_ALL_VARIANTS)
+     ggml_add_cpu_backend_variant(skylakex       AVX F16C AVX2 FMA AVX512)
+     ggml_add_cpu_backend_variant(icelake        AVX F16C AVX2 FMA AVX512 AVX512_VBMI AVX512_VNNI)
+     ggml_add_cpu_backend_variant(alderlake      AVX F16C AVX2 FMA AVX_VNNI)
+-    if (NOT MSVC)
+-        # MSVC doesn't support AMX
+-        ggml_add_cpu_backend_variant(sapphirerapids AVX F16C AVX2 FMA AVX512 AVX512_VBMI AVX512_VNNI AVX512_BF16 AMX_TILE AMX_INT8)
+-    endif()
+ else ()
+     ggml_add_cpu_backend_variant_impl("")
+ endif()

ml/backend/ggml/ggml/src/CMakeLists.txt

@@ -293,10 +293,6 @@ if (GGML_CPU_ALL_VARIANTS)
     ggml_add_cpu_backend_variant(skylakex       AVX F16C AVX2 FMA AVX512)
     ggml_add_cpu_backend_variant(icelake        AVX F16C AVX2 FMA AVX512 AVX512_VBMI AVX512_VNNI)
     ggml_add_cpu_backend_variant(alderlake      AVX F16C AVX2 FMA AVX_VNNI)
-    if (NOT MSVC)
-        # MSVC doesn't support AMX
-        ggml_add_cpu_backend_variant(sapphirerapids AVX F16C AVX2 FMA AVX512 AVX512_VBMI AVX512_VNNI AVX512_BF16 AMX_TILE AMX_INT8)
-    endif()
 else ()
     ggml_add_cpu_backend_variant_impl("")
 endif()