feat: support building with upstream ggml (#1999)

cmake/ggml.cmake

@@ -0,0 +1,27 @@
+if(NOT TARGET ggml AND NOT TARGET ggml::ggml)
+    if(SD_USE_SYSTEM_GGML)
+        find_package(ggml REQUIRED)
+    else()
+        add_subdirectory("${SD_GGML_SOURCE_DIR}" "${CMAKE_CURRENT_BINARY_DIR}/ggml")
+    endif()
+endif()
+if(NOT TARGET ggml)
+    add_library(ggml ALIAS ggml::ggml)
+endif()
+
+get_target_property(sd_ggml_imported ggml IMPORTED)
+if(sd_ggml_imported)
+    set(sd_ggml_private_include "${SD_GGML_SOURCE_DIR}/src")
+else()
+    get_target_property(sd_ggml_private_include ggml SOURCE_DIR)
+endif()
+if(NOT EXISTS "${sd_ggml_private_include}/ggml-impl.h")
+    message(FATAL_ERROR "Set SD_GGML_SOURCE_DIR to the source tree matching the selected ggml library (ggml-impl.h is required).")
+endif()
+target_include_directories(${SD_LIB} PRIVATE "${sd_ggml_private_include}")
+set_property(TARGET ${SD_LIB} PROPERTY SD_GGML_PRIVATE_INCLUDE_DIR "${sd_ggml_private_include}")
+
+if(SD_USE_UPSTREAM_GGML)
+    target_compile_definitions(${SD_LIB} PUBLIC SD_USE_UPSTREAM_GGML)
+    message(WARNING "Using upstream GGML: FP8 and INT8 tensorwise/convrot are disabled. Some operators may be unsupported and performance may be lower than with patched GGML.")
+endif()