tests : enable test-chat out of tree build (ggml-org#19558)

The binary relies on model files that it tries to find. However, when
configuring the build directory to be parallel to the source tree those
heuristics fail.

This sets the working directory for the test executable to be the
source-tree which resolves this issue.

Author: jplehr

tests/CMakeLists.txt

@@ -152,7 +152,7 @@ if (NOT WIN32 OR NOT BUILD_SHARED_LIBS)
     llama_build_and_test(test-grammar-parser.cpp)
     llama_build_and_test(test-grammar-integration.cpp)
     llama_build_and_test(test-llama-grammar.cpp)
-    llama_build_and_test(test-chat.cpp)
+    llama_build_and_test(test-chat.cpp WORKING_DIRECTORY ${PROJECT_SOURCE_DIR})
     # TODO: disabled on loongarch64 because the ggml-ci node lacks Python 3.8
     if (NOT ${CMAKE_SYSTEM_PROCESSOR} MATCHES "loongarch64")
         llama_build_and_test(test-json-schema-to-grammar.cpp   WORKING_DIRECTORY ${PROJECT_SOURCE_DIR})