bindings-ruby : enable setting of flash-attn

This commit enables the flast_attn context parameter to be set in the
Ruby bindings.

The motivation for this is that the default setting for this recently
changed to true, which causes the following test to fail:
```console
Failure: test_transcribe_n_processors(TestWhisper):
  </ask not what your country can do for you[,.] ask what you can do for your country/i> was expected to be =~
  <" And so, my fellow Americans! Ask not what you do. what your country can do for you. Ask what you can do for your country.">.
```
An alternative could also be to change the test.

Author: danbev

bindings/ruby/ext/ruby_whisper_context.c

@@ -118,22 +118,34 @@ ruby_whisper_normalize_model_path(VALUE model_path)
  *   new("base.en") -> Whisper::Context
  *   new("path/to/model.bin") -> Whisper::Context
  *   new(Whisper::Model::URI.new("https://example.net/uri/of/model.bin")) -> Whisper::Context
+ *   new("base.en", flash_attn: false) -> Whisper::Context
  */
 static VALUE
 ruby_whisper_initialize(int argc, VALUE *argv, VALUE self)
 {
   ruby_whisper *rw;
-  VALUE whisper_model_file_path;
+  VALUE whisper_model_file_path, options;
+  VALUE flash_attn_opt;
 
   // TODO: we can support init from buffer here too maybe another ruby object to expose
-  rb_scan_args(argc, argv, "01", &whisper_model_file_path);
+  rb_scan_args(argc, argv, "01:", &whisper_model_file_path, &options);
   TypedData_Get_Struct(self, ruby_whisper, &ruby_whisper_type, rw);
 
   whisper_model_file_path = ruby_whisper_normalize_model_path(whisper_model_file_path);
   if (!rb_respond_to(whisper_model_file_path, id_to_s)) {
     rb_raise(rb_eRuntimeError, "Expected file path to model to initialize Whisper::Context");
   }
-  rw->context = whisper_init_from_file_with_params(StringValueCStr(whisper_model_file_path), whisper_context_default_params());
+
+  struct whisper_context_params cparams = whisper_context_default_params();
+
+  if (!NIL_P(options)) {
+    flash_attn_opt = rb_hash_aref(options, ID2SYM(rb_intern("flash_attn")));
+    if (!NIL_P(flash_attn_opt)) {
+      cparams.flash_attn = (flash_attn_opt == Qtrue);
+    }
+  }
+
+  rw->context = whisper_init_from_file_with_params(StringValueCStr(whisper_model_file_path), cparams);
   if (rw->context == NULL) {
     rb_raise(rb_eRuntimeError, "error: failed to initialize whisper context");
   }

bindings/ruby/test/test_whisper.rb

@@ -30,7 +30,7 @@ def test_transcribe_non_parallel
   end
 
   def test_transcribe_n_processors
-    @whisper = Whisper::Context.new("base.en")
+    @whisper = Whisper::Context.new("base.en", flash_attn: false)
     params  = Whisper::Params.new
 
     @whisper.transcribe(AUDIO, params, n_processors: 4) {|text|