cmake: fix ggml-shaders-gen compiler paths containing spaces (#12747)

fixes error for compiler paths with spaces

ggml/src/ggml-vulkan/cmake/host-toolchain.cmake.in

@@ -4,8 +4,8 @@ set(CMAKE_CXX_FLAGS -O2)
 set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
 set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY NEVER)
 set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE NEVER)
-set(CMAKE_C_COMPILER @HOST_C_COMPILER@)
-set(CMAKE_CXX_COMPILER @HOST_CXX_COMPILER@)
+set(CMAKE_C_COMPILER "@HOST_C_COMPILER@")
+set(CMAKE_CXX_COMPILER "@HOST_CXX_COMPILER@")
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY @CMAKE_RUNTIME_OUTPUT_DIRECTORY@)
 
 if("@CMAKE_C_COMPILER_ID@" STREQUAL "MSVC")