metal : allow env metal variable to override resource path (#1415)

* Allow env variable to override resource path

* Update ggml-metal.m

---------

Co-authored-by: Georgi Gerganov <[email protected]>

Author: codesoda

ggml-metal.m

@@ -210,7 +210,13 @@ static void ggml_metal_log(enum ggml_log_level level, const char* format, ...){
         } else {
             GGML_METAL_LOG_INFO("%s: default.metallib not found, loading from source\n", __func__);
 
-            NSString * sourcePath = [bundle pathForResource:@"ggml-metal" ofType:@"metal"];
+            NSString * sourcePath;
+            NSString * ggmlMetalPathResources = [[NSProcessInfo processInfo].environment objectForKey:@"GGML_METAL_PATH_RESOURCES"];
+            if (ggmlMetalPathResources) {
+                sourcePath = [ggmlMetalPathResources stringByAppendingPathComponent:@"ggml-metal.metal"];
+            } else {
+                sourcePath = [bundle pathForResource:@"ggml-metal" ofType:@"metal"];
+            }
             if (sourcePath == nil) {
                 GGML_METAL_LOG_WARN("%s: error: could not use bundle path to find ggml-metal.metal, falling back to trying cwd\n", __func__);
                 sourcePath = @"ggml-metal.metal";