cmake: Add GGML_BMI2 build option

Author: remyoudompheng

ggml/CMakeLists.txt

@@ -106,6 +106,7 @@ option(GGML_CPU_KLEIDIAI     "ggml: use KleidiAI optimized kernels if applicable
 option(GGML_AVX              "ggml: enable AVX"              ${INS_ENB})
 option(GGML_AVX_VNNI         "ggml: enable AVX-VNNI"         OFF)
 option(GGML_AVX2             "ggml: enable AVX2"             ${INS_ENB})
+option(GGML_BMI2             "ggml: enable BMI2"             ${INS_ENB})
 option(GGML_AVX512           "ggml: enable AVX512F"          OFF)
 option(GGML_AVX512_VBMI      "ggml: enable AVX512-VBMI"      OFF)
 option(GGML_AVX512_VNNI      "ggml: enable AVX512-VNNI"      OFF)

ggml/src/ggml-cpu/CMakeLists.txt

@@ -233,6 +233,10 @@ function(ggml_add_cpu_backend_variant_impl tag_name)
                     list(APPEND ARCH_FLAGS -mfma)
                     list(APPEND ARCH_DEFINITIONS GGML_FMA)
                 endif()
+                if (GGML_BMI2)
+                    list(APPEND ARCH_FLAGS -mbmi2)
+                    list(APPEND ARCH_DEFINITIONS GGML_BMI2)
+                endif()
                 if (GGML_AVX)
                     list(APPEND ARCH_FLAGS -mavx)
                     list(APPEND ARCH_DEFINITIONS GGML_AVX)