Reduce default thread stack size to 64KB (#19043)

Author: kleisauke

system/lib/libc/musl/src/internal/pthread_impl.h

@@ -251,7 +251,7 @@ extern hidden unsigned __default_guardsize;
 
 #ifdef __EMSCRIPTEN__
 // Keep in sync with DEFAULT_PTHREAD_STACK_SIZE in settings.js
-#define DEFAULT_STACK_SIZE (2*1024*1024)
+#define DEFAULT_STACK_SIZE (64*1024)
 #else
 #define DEFAULT_STACK_SIZE 131072
 #endif

test/other/test_default_pthread_stack_size.c

@@ -8,7 +8,7 @@ int main() {
   size_t stacksize;
   pthread_attr_getstacksize(&attr, &stacksize);
   printf("%zu\n", stacksize);
-  // Should match DEFAULT_PTHREAD_STACK_SIZE = 2*1024*1024;
-  assert(stacksize == 2*1024*1024);
+  // Should match DEFAULT_PTHREAD_STACK_SIZE = 64*1024;
+  assert(stacksize == 64*1024);
   return 0;
 }