shared/runtime/pyexec: Set __file__ for file input when enabled.

When `MICROPY_MODULE___FILE__` is enabled and parsing file input, set the
global `__file__` variable to the source filename. This matches the
behavior of the unix port and provides the current filename to the
executing script.

Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

shared/runtime/pyexec.c

@@ -103,6 +103,11 @@ static int parse_compile_execute(const void *source, mp_parse_input_kind_t input
             }
             // source is a lexer, parse and compile the script
             qstr source_name = lex->source_name;
+            #if MICROPY_MODULE___FILE__
+            if (input_kind == MP_PARSE_FILE_INPUT) {
+                mp_store_global(MP_QSTR___file__, MP_OBJ_NEW_QSTR(source_name));
+            }
+            #endif
             mp_parse_tree_t parse_tree = mp_parse(lex, input_kind);
             #if defined(MICROPY_UNIX_COVERAGE)
             // allow to print the parse tree in the coverage build