fix: ggml: fix vulkan-shaders-gen build

The vulkan-shaders-gen target was not being built correctly
in case of cross-compilation.
Other outputs need to be built for the cross compile target,
but vulkan-shaders-gen needs to be built for the host.

ggml/src/CMakeLists.txt

@@ -652,16 +652,43 @@ if (GGML_VULKAN)
             add_compile_definitions(GGML_VULKAN_RUN_TESTS)
         endif()
 
-        add_subdirectory(vulkan-shaders)
-
-        set (_ggml_vk_genshaders_cmd vulkan-shaders-gen)
+        if (NOT CMAKE_CROSSCOMPILING)
+            add_subdirectory(vulkan-shaders)
+        else()
+            include(ExternalProject)
+            # Native build through ExternalProject_Add
+            ExternalProject_Add(
+                vulkan-shaders-gen
+                SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/vulkan-shaders
+                CMAKE_ARGS -DCMAKE_BUILD_TYPE=Release
+                        -DCMAKE_INSTALL_PREFIX=${CMAKE_BINARY_DIR}
+                        -DCMAKE_TOOLCHAIN_FILE=
+                        -DCMAKE_SYSROOT=
+                        -DCMAKE_C_FLAGS=-O2
+                        -DCMAKE_CXX_FLAGS=-O2
+                        -DCMAKE_FIND_ROOT_PATH_MODE_PROGRAM=NEVER
+                        -DCMAKE_FIND_ROOT_PATH_MODE_LIBRARY=NEVER
+                        -DCMAKE_FIND_ROOT_PATH_MODE_INCLUDE=NEVER
+                        -DCMAKE_C_COMPILER=gcc
+                        -DCMAKE_CXX_COMPILER=g++
+                BUILD_COMMAND ${CMAKE_COMMAND} --build .
+                INSTALL_COMMAND ${CMAKE_COMMAND} --install .
+                INSTALL_DIR ${CMAKE_BINARY_DIR}
+            )
+            ExternalProject_Add_StepTargets(vulkan-shaders-gen build install)
+        endif()
+        set (_ggml_vk_genshaders_cmd ${CMAKE_BINARY_DIR}/bin/vulkan-shaders-gen)
         set (_ggml_vk_header     ${CMAKE_CURRENT_BINARY_DIR}/ggml-vulkan-shaders.hpp)
         set (_ggml_vk_source     ${CMAKE_CURRENT_BINARY_DIR}/ggml-vulkan-shaders.cpp)
         set (_ggml_vk_input_dir  ${CMAKE_CURRENT_SOURCE_DIR}/vulkan-shaders)
         set (_ggml_vk_output_dir ${CMAKE_CURRENT_BINARY_DIR}/vulkan-shaders.spv)
 
         file(GLOB _ggml_vk_shader_deps "${_ggml_vk_input_dir}/*.comp")
 
+        if (CMAKE_CROSSCOMPILING)
+            set(_ggml_vk_shader_deps ${_ggml_vk_shader_deps} vulkan-shaders-gen-build vulkan-shaders-gen-install)
+        endif()
+
         add_custom_command(
             OUTPUT ${_ggml_vk_header}
                    ${_ggml_vk_source}

ggml/src/vulkan-shaders/CMakeLists.txt

@@ -1,7 +1,14 @@
+cmake_minimum_required(VERSION 3.12)
+project(vulkan-shaders-gen C CXX)
+
 find_package (Threads REQUIRED)
 
 set(TARGET vulkan-shaders-gen)
 add_executable(${TARGET} vulkan-shaders-gen.cpp)
-install(TARGETS ${TARGET} RUNTIME)
+if (${CMAKE_RUNTIME_OUTPUT_DIRECTORY})
+    install(TARGETS ${TARGET} RUNTIME)
+else()
+    install(TARGETS ${TARGET} RUNTIME DESTINATION bin)
+endif()
 target_compile_features(${TARGET} PRIVATE cxx_std_11)
 target_link_libraries(vulkan-shaders-gen PUBLIC Threads::Threads)