py: the entire `<unistd.h>` shouldn't be needed

py/emitcommon.c

@@ -1,4 +1,4 @@
-#include <unistd.h>
+#include <string.h>
 #include <stdint.h>
 #include <assert.h>
 

py/stream.c

@@ -1,4 +1,4 @@
-#include <unistd.h>
+#include <string.h>
 
 #include "nlr.h"
 #include "misc.h"