cmake: Enable building against system ggml

This facilitates package maintenance for Linux distributions, where the
libggml library most likely will be shipped as an individual package
upon which a llama.cpp package depends.

CMakeLists.txt

@@ -29,6 +29,8 @@ else()
     set(LLAMA_STANDALONE OFF)
 endif()
 
+option(LLAMA_USE_SYSTEM_GGML "Use system libggml" OFF)
+
 if (EMSCRIPTEN)
     set(BUILD_SHARED_LIBS_DEFAULT OFF)
 
@@ -145,7 +147,15 @@ endif()
 # 3rd-party
 #
 
-if (NOT TARGET ggml)
+if (LLAMA_USE_SYSTEM_GGML)
+    message(STATUS "Using system-provided libggml, skipping ggml build")
+    find_package(ggml REQUIRED)
+    set(GGML_TARGET ggml::ggml)
+else()
+    set(GGML_TARGET ggml)
+endif()
+
+if (NOT TARGET ggml AND NOT LLAMA_USE_SYSTEM_GGML)
     add_subdirectory(ggml)
     # ... otherwise assume ggml is added by a parent CMakeLists.txt
 endif()

examples/gguf-hash/CMakeLists.txt

@@ -18,5 +18,5 @@ endif()
 add_library(sha256 OBJECT deps/sha256/sha256.c deps/sha256/sha256.h)
 target_link_libraries(${TARGET} PRIVATE sha256)
 
-target_link_libraries(${TARGET} PRIVATE ggml ${CMAKE_THREAD_LIBS_INIT})
+target_link_libraries(${TARGET} PRIVATE ${GGML_TARGET} ${CMAKE_THREAD_LIBS_INIT})
 target_compile_features(${TARGET} PRIVATE cxx_std_17)

examples/gguf/CMakeLists.txt

@@ -1,5 +1,5 @@
 set(TARGET llama-gguf)
 add_executable(${TARGET} gguf.cpp)
 install(TARGETS ${TARGET} RUNTIME)
-target_link_libraries(${TARGET} PRIVATE ggml ${CMAKE_THREAD_LIBS_INIT})
+target_link_libraries(${TARGET} PRIVATE ${GGML_TARGET} ${CMAKE_THREAD_LIBS_INIT})
 target_compile_features(${TARGET} PRIVATE cxx_std_17)

examples/llava/CMakeLists.txt

@@ -5,7 +5,7 @@ add_library(llava OBJECT
             clip.h
             )
 
-target_link_libraries(llava PRIVATE ggml llama ${CMAKE_THREAD_LIBS_INIT})
+target_link_libraries(llava PRIVATE ${GGML_TARGET} llama ${CMAKE_THREAD_LIBS_INIT})
 
 target_include_directories(llava PUBLIC .)
 target_include_directories(llava PUBLIC ../..)
@@ -18,7 +18,7 @@ if (BUILD_SHARED_LIBS)
     set_target_properties(llava PROPERTIES POSITION_INDEPENDENT_CODE ON)
     target_compile_definitions(llava PRIVATE LLAMA_SHARED LLAMA_BUILD)
     add_library(llava_shared SHARED $<TARGET_OBJECTS:llava>)
-    target_link_libraries(llava_shared PRIVATE ggml llama ${CMAKE_THREAD_LIBS_INIT})
+    target_link_libraries(llava_shared PRIVATE ${GGML_TARGET} llama ${CMAKE_THREAD_LIBS_INIT})
     install(TARGETS llava_shared LIBRARY)
 endif()
 

examples/rpc/CMakeLists.txt

@@ -1,2 +1,2 @@
 add_executable(rpc-server rpc-server.cpp)
-target_link_libraries(rpc-server PRIVATE ggml llama)
+target_link_libraries(rpc-server PRIVATE ${GGML_TARGET} llama)

src/CMakeLists.txt

@@ -32,7 +32,7 @@ add_library(llama
 target_include_directories(llama PUBLIC . ../include ../common)
 target_compile_features   (llama PUBLIC cxx_std_17) # don't bump
 
-target_link_libraries(llama PUBLIC ggml)
+target_link_libraries(llama PUBLIC ${GGML_TARGET})
 
 if (BUILD_SHARED_LIBS)
     set_target_properties(llama PROPERTIES POSITION_INDEPENDENT_CODE ON)