[mimalloc] Prefer emscripten_err in _mi_prim_out_stderr. NFC

This function maps directly to stderr under node which is more direct
than console.error and better in workers.

Author: sbc100

system/lib/mimalloc/src/prim/emscripten/prim.c

@@ -47,7 +47,7 @@ terms of the MIT license. A copy of the license can be found in the file
 // init
 //---------------------------------------------
 
-void _mi_prim_mem_init( mi_os_mem_config_t* config) {
+void _mi_prim_mem_init(mi_os_mem_config_t* config) {
   config->page_size = 64*MI_KiB; // WebAssembly has a fixed page size: 64KiB
   config->alloc_granularity = 16;
   config->has_overcommit = false;
@@ -168,8 +168,8 @@ void _mi_prim_process_info(mi_process_info_t* pinfo)
 
 #include <emscripten/console.h>
 
-void _mi_prim_out_stderr( const char* msg) {
-  emscripten_console_error(msg);
+void _mi_prim_out_stderr(const char* msg) {
+  emscripten_err(msg);
 }