cmake : allow user to override default options (ggerganov#8178)

CMakeLists.txt

@@ -79,8 +79,15 @@ set(GGML_SANITIZE_ADDRESS   ${LLAMA_SANITIZE_ADDRESS})
 set(GGML_SANITIZE_UNDEFINED ${LLAMA_SANITIZE_UNDEFINED})
 set(GGML_ALL_WARNINGS       ${LLAMA_ALL_WARNINGS})
 set(GGML_FATAL_WARNINGS     ${LLAMA_FATAL_WARNINGS})
-set(GGML_LLAMAFILE          ON)
-set(GGML_CUDA_USE_GRAPHS    ON)
+
+# change the default for these ggml options
+if (NOT DEFINED GGML_LLAMAFILE)
+    set(GGML_LLAMAFILE ON)
+endif()
+
+if (NOT DEFINED GGML_CUDA_USE_GRAPHS)
+    set(GGML_CUDA_USE_GRAPHS ON)
+endif()
 
 # transition helpers
 function (llama_option_depr TYPE OLD NEW)