cmake : fix PowerPC build (ggml-org#12241)

Closes ggml-org#12240

Author: mehendarkarprajwal

ggml/src/ggml-cpu/CMakeLists.txt

@@ -287,17 +287,25 @@ function(ggml_add_cpu_backend_variant_impl tag_name)
                 endif()
             endif()
         endif()
-    elseif (${CMAKE_SYSTEM_PROCESSOR} MATCHES "ppc64")
+    elseif ("${CMAKE_SYSTEM_PROCESSOR} " STREQUAL "ppc64le " OR "${CMAKE_SYSTEM_PROCESSOR} " STREQUAL "powerpc ")
         message(STATUS "PowerPC detected")
-        execute_process(COMMAND bash -c "grep POWER /proc/cpuinfo | head -n 1" OUTPUT_VARIABLE POWER_M)
-        if (${POWER_M} MATCHES "POWER10")
-            list(APPEND ARCH_FLAGS -mcpu=power10)
-        elseif (${POWER_M} MATCHES "POWER9")
-            list(APPEND ARCH_FLAGS -mcpu=power9)
+        if(${CMAKE_SYSTEM_PROCESSOR} MATCHES "ppc64")
+            file(READ "/proc/cpuinfo" POWER10_M)
+        elseif(${CMAKE_SYSTEM_PROCESSOR} MATCHES "powerpc")
+            execute_process(COMMAND bash -c "prtconf |grep 'Implementation' | head -n 1" OUTPUT_VARIABLE POWER10_M)
+        endif()
+
+        string(REGEX MATCHALL "POWER *([0-9]+)" MATCHED_STRING "${POWER10_M}")
+        string(REGEX REPLACE "POWER *([0-9]+)" "\\1" EXTRACTED_NUMBER "${MATCHED_STRING}")
+
+        if (EXTRACTED_NUMBER GREATER_EQUAL 10)
+            list(APPEND ARCH_FLAGS -mcpu=power10 -mpowerpc64)
+        elseif (EXTRACTED_NUMBER EQUAL 9)
+            list(APPEND ARCH_FLAGS -mcpu=power9 -mpowerpc64)
         elseif (${CMAKE_SYSTEM_PROCESSOR} MATCHES "ppc64le")
             list(APPEND ARCH_FLAGS -mcpu=powerpc64le -mtune=native)
         else()
-            list(APPEND ARCH_FLAGS -mcpu=powerpc64 -mtune=native)
+            list(APPEND ARCH_FLAGS -mcpu=native -mtune=native -mpowerpc64)
         endif()
     elseif (${CMAKE_SYSTEM_PROCESSOR} MATCHES "loongarch64")
         message(STATUS "loongarch64 detected")