llama : Add Gemma 3 support (+ experimental vision capability) (#12343)

* llama : Add Gemma 3 text-only support

* fix python coding style

* fix compile on ubuntu

* python: fix style

* fix ubuntu compile

* fix build on ubuntu (again)

* fix ubuntu build, finally

* clip : Experimental support for Gemma 3 vision (#12344)

* clip : Experimental support for Gemma 3 vision

* fix build

* PRId64

examples/llava/README-gemma3.md

@@ -0,0 +1,30 @@
+# Gemma 3 vision
+
+> [!IMPORTANT]
+>
+> This is very experimental, only used for demo purpose.
+
+## How to get mmproj.gguf?
+
+```bash
+cd gemma-3-4b-it
+python ../llama.cpp/examples/llava/gemma3_convert_encoder_to_gguf.py .
+
+# output file is mmproj.gguf
+```
+
+## How to run it?
+
+What you need:
+- The text model GGUF, can be converted using `convert_hf_to_gguf.py`
+- The mmproj file from step above
+- An image file
+
+```bash
+# build
+cmake -B build
+cmake --build build --target llama-gemma3-cli
+
+# run it
+./build/bin/llama-gemma3-cli -m {text_model}.gguf --mmproj mmproj.gguf --image your_image.jpg
+```