py/py.mk: Ignore USER_C_MODULES check when building mpy-cross.

Signed-off-by: Andrew Leech <[email protected]>

Author: pi-anl

py/py.mk

@@ -33,8 +33,11 @@ ifneq ($(USER_C_MODULES),)
 # pre-define USERMOD variables as expanded so that variables are immediate
 # expanded as they're added to them
 
-# Confirm the provided path exists, show abspath if not to make it clearer to fix.
+# Confirm the provided path exists, show abspath if not to make it clearer to fix. Check skipped for mpy-cross build.
+ifneq ($(PROG),mpy-cross)
 $(if $(wildcard $(USER_C_MODULES)/.),,$(error USER_C_MODULES doesn't exist: $(abspath $(USER_C_MODULES))))
+endif
+
 
 # C/C++ files that are included in the QSTR/module build
 SRC_USERMOD_C :=