Fix x86 tests (#1691)

* fix x86 tests

* comment

mlx/backend/common/CMakeLists.txt

@@ -10,7 +10,7 @@ add_custom_command(
   COMMAND
     /bin/bash ${CMAKE_CURRENT_SOURCE_DIR}/make_compiled_preamble.sh
     ${CMAKE_CURRENT_BINARY_DIR}/compiled_preamble.cpp ${COMPILER}
-    ${PROJECT_SOURCE_DIR} ${CLANG}
+    ${PROJECT_SOURCE_DIR} ${CLANG} ${CMAKE_SYSTEM_PROCESSOR}
   DEPENDS make_compiled_preamble.sh
           compiled_preamble.h
           ${PROJECT_SOURCE_DIR}/mlx/types/half_types.h

mlx/backend/common/make_compiled_preamble.sh

@@ -10,15 +10,16 @@ OUTPUT_FILE=$1
 GCC=$2
 SRCDIR=$3
 CLANG=$4
+ARCH=$5
 
 if [ "$CLANG" = "TRUE" ]; then
   read -r -d '' INCLUDES <<- EOM
-  #include <cmath>
-  #include <complex>
-  #include <cstdint>
-  #include <vector>
+#include <cmath>
+#include <complex>
+#include <cstdint>
+#include <vector>
 EOM
-CC_FLAGS=""
+CC_FLAGS="-arch ${ARCH}"
 else
 CC_FLAGS="-std=c++17"
 fi