cmake : do not include ./src as public for libllama (#13062)

* cmake : do not include ./src as public for libllama

ggml-ci

* cmake : rework tests

ggml-ci

* llguidance : remove unicode include

ggml-ci

* cmake : make c++17 private

ggml-ci

tests/test-grammar-integration.cpp

@@ -2,10 +2,11 @@
 #undef NDEBUG
 #endif
 
-#include "unicode.h"
-#include "llama-grammar.h"
 #include "json-schema-to-grammar.h"
 
+#include "../src/unicode.h"
+#include "../src/llama-grammar.h"
+
 #include <cassert>
 #include <string>
 #include <vector>