cmake: add ggml find package (#11369)

* Add initial ggml cmake package

* Add build numbers to ggml find-package

* Expand variables with GGML_ prefix

* Guard against adding to cache variable twice

* Add git to msys2 workflow

* Handle ggml-cpu-* variants

* Link ggml/ggml-base libraries to their targets

* Replace main-cmake-pkg with simple-cmake-pkg

* Interface features require c_std_90

* Fix typo

* Removed unnecessary bracket from status message

* Update examples/simple-cmake-pkg/README.md

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* Update examples/simple-cmake-pkg/README.md

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

examples/simple-cmake-pkg/README.md

@@ -0,0 +1,34 @@
+# llama.cpp/example/simple-cmake-pkg
+
+This program builds [simple](../simple) using a relocatable CMake package. It serves as an example of using the `find_package()` CMake command to conveniently include [llama.cpp](https://github.com/ggerganov/llama.cpp) in projects which live outside of the source tree.
+
+## Building
+
+Because this example is "outside of the source tree", it is important to first build/install llama.cpp using CMake. An example is provided here, but please see the [llama.cpp build instructions](../..) for more detailed build instructions.
+
+### Considerations
+
+When hardware acceleration libraries are used (e.g. CUDA, Metal, Vulkan, etc.), the appropriate dependencies will be searched for automatically. So, for example, when finding a package
+
+### Build llama.cpp and install to llama.cpp/inst
+
+```sh
+git clone https://github.com/ggerganov/llama.cpp
+cd llama.cpp
+cmake -S . -B build
+cmake --build build
+cmake --install build --prefix inst
+
+### Build simple-cmake-pkg
+
+```sh
+cd examples/simple-cmake-pkg
+cmake -S . -B build -DCMAKE_PREFIX_PATH=../../inst/lib/cmake
+cmake --build build
+```
+
+### Run simple-cmake-pkg
+
+```sh
+./build/llama-simple-cmake-pkg -m ./models/llama-7b-v2/ggml-model-f16.gguf "Hello my name is"
+```