code_size_compare.py: add prompt for unsupported arch and config

Add prompt message for a series of supported combination of
architecture and configuration when someone tries unsupported
combinations.

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
diff --git a/scripts/code_size_compare.py b/scripts/code_size_compare.py
index e61236a..b8f2942 100755
--- a/scripts/code_size_compare.py
+++ b/scripts/code_size_compare.py
@@ -71,6 +71,14 @@
     infer build command for code size measurement.
     """
 
+    SupportedArchConfig = [
+        "-a " + SupportedArch.AARCH64.value + " -c " + SupportedConfig.DEFAULT.value,
+        "-a " + SupportedArch.AARCH32.value + " -c " + SupportedConfig.DEFAULT.value,
+        "-a " + SupportedArch.X86_64.value  + " -c " + SupportedConfig.DEFAULT.value,
+        "-a " + SupportedArch.X86.value     + " -c " + SupportedConfig.DEFAULT.value,
+        "-a " + SupportedArch.ARMV8_M.value + " -c " + SupportedConfig.TFM_MEDIUM.value,
+    ]
+
     def __init__(self, arch: str, config: str) -> None:
         """
         arch: architecture to measure code size on.
@@ -96,6 +104,9 @@
         else:
             print("Unsupported architecture: {} and configurations: {}"
                   .format(self.arch, self.config))
+            print("\nPlease use supported combination of architecture and configuration:")
+            for comb in CodeSizeInfo.SupportedArchConfig:
+                print(comb)
             sys.exit(1)