darwin: Fix sysroot on simulator (#809)

The assumption that dyld_sim is the first loaded image is no longer
true. Fix by making one more pass before indexing loaded images.

gum/backend-darwin/gumdarwinmoduleresolver.c

@@ -35,6 +35,8 @@ static void gum_darwin_module_resolver_get_property (GObject * object,
 static void gum_darwin_module_resolver_set_property (GObject * object,
     guint property_id, const GValue * value, GParamSpec * pspec);
 
+static gboolean gum_find_sysroot (const GumModuleDetails * details,
+    gpointer user_data);
 static gboolean gum_store_module (const GumModuleDetails * details,
     gpointer user_data);
 
@@ -165,6 +167,7 @@ gum_darwin_module_resolver_load (GumDarwinModuleResolver * self,
   ctx.sysroot = NULL;
   ctx.sysroot_length = 0;
 
+  gum_darwin_enumerate_modules (self->task, gum_find_sysroot, &ctx);
   gum_darwin_enumerate_modules (self->task, gum_store_module, &ctx);
   if (ctx.index == 0)
     goto invalid_task;
@@ -382,19 +385,29 @@ gum_darwin_module_resolver_find_dynamic_address (GumDarwinModuleResolver * self,
 }
 
 static gboolean
-gum_store_module (const GumModuleDetails * details,
+gum_find_sysroot (const GumModuleDetails * details,
                   gpointer user_data)
 {
   GumCollectModulesContext * ctx = user_data;
-  GumDarwinModuleResolver * self = ctx->self;
-  GumDarwinModule * module;
 
-  if (ctx->index == 0 && g_str_has_suffix (details->path, "/usr/lib/dyld_sim"))
+  if (g_str_has_suffix (details->path, "/usr/lib/dyld_sim"))
   {
     ctx->sysroot_length = strlen (details->path) - 17;
     ctx->sysroot = g_strndup (details->path, ctx->sysroot_length);
+    return FALSE;
   }
 
+  return TRUE;
+}
+
+static gboolean
+gum_store_module (const GumModuleDetails * details,
+                  gpointer user_data)
+{
+  GumCollectModulesContext * ctx = user_data;
+  GumDarwinModuleResolver * self = ctx->self;
+  GumDarwinModule * module;
+
   module = gum_darwin_module_new_from_memory (details->path, self->task,
       details->range->base_address, GUM_DARWIN_MODULE_FLAGS_NONE, NULL);
   g_hash_table_insert (self->modules, g_strdup (details->name),