lib/utils/pyexec: Add pyexec_file_if_exists() helper function.

It will only execute the script if it can be stat'd and is a file.

lib/utils/pyexec.c

@@ -541,6 +541,14 @@ int pyexec_file(const char *filename) {
     return parse_compile_execute(filename, MP_PARSE_FILE_INPUT, EXEC_FLAG_SOURCE_IS_FILENAME);
 }
 
+int pyexec_file_if_exists(const char *filename) {
+    mp_import_stat_t stat = mp_import_stat(filename);
+    if (stat != MP_IMPORT_STAT_FILE) {
+        return 1; // success (no file is the same as an empty file executing without fail)
+    }
+    return pyexec_file(filename);
+}
+
 #if MICROPY_MODULE_FROZEN
 int pyexec_frozen_module(const char *name) {
     void *frozen_data;

lib/utils/pyexec.h

@@ -46,6 +46,7 @@ extern int pyexec_system_exit;
 int pyexec_raw_repl(void);
 int pyexec_friendly_repl(void);
 int pyexec_file(const char *filename);
+int pyexec_file_if_exists(const char *filename);
 int pyexec_frozen_module(const char *name);
 void pyexec_event_repl_init(void);
 int pyexec_event_repl_process_char(int c);