code_size_compare: detect architecture of x86_32 properly

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
diff --git a/scripts/code_size_compare.py b/scripts/code_size_compare.py
index cc43dc7..3b988a6 100755
--- a/scripts/code_size_compare.py
+++ b/scripts/code_size_compare.py
@@ -147,7 +147,7 @@
         return SupportedArch.AARCH32.value
     if '__x86_64__' in cc_output:
         return SupportedArch.X86_64.value
-    if '__x86__' in cc_output:
+    if '__i386__' in cc_output:
         return SupportedArch.X86.value
     else:
         print("Unknown host architecture, cannot auto-detect arch.")