simplify cmake due to minimum project requirement already gone to 3.12

CMakeLists.txt

@@ -48,31 +48,27 @@ set(INSTALL_LIB_DIR      "${CMAKE_CURRENT_LIST_DIR}" CACHE PATH "Path where lib
 set(INSTALL_INCLUDE_DIR  "include/darknet"           CACHE PATH "Path where headers will be installed")
 set(INSTALL_CMAKE_DIR    "share/darknet"             CACHE PATH "Path where cmake configs will be installed")
 
-if(${CMAKE_VERSION} VERSION_LESS "3.9.0")
-  message(WARNING "To build with CUDA support you need CMake 3.9.0+")
-  set(ENABLE_CUDA "FALSE" CACHE BOOL "Enable CUDA support" FORCE)
-else()
-  include(CheckLanguage)
-  check_language(CUDA)
-  if(CMAKE_CUDA_COMPILER AND ENABLE_CUDA)
-    set(CUDA_ARCHITECTURES "Auto" CACHE STRING "\"Auto\" detects local machine GPU compute arch at runtime, \"Common\" and \"All\" cover common and entire subsets of architectures, \"Names\" is a list of architectures to enable by name, \"Numbers\" is a list of compute capabilities (version number) to enable")
-    set_property(CACHE CUDA_ARCHITECTURES PROPERTY STRINGS "Auto" "Common" "All" "Kepler Maxwell Kepler+Tegra Maxwell+Tegra Pascal" "3.0 7.5")
-    enable_language(CUDA)
+include(CheckLanguage)
+check_language(CUDA)
+if(CMAKE_CUDA_COMPILER AND ENABLE_CUDA)
+  set(CUDA_ARCHITECTURES "Auto" CACHE STRING "\"Auto\" detects local machine GPU compute arch at runtime, \"Common\" and \"All\" cover common and entire subsets of architectures, \"Names\" is a list of architectures to enable by name, \"Numbers\" is a list of compute capabilities (version number) to enable")
+  set_property(CACHE CUDA_ARCHITECTURES PROPERTY STRINGS "Auto" "Common" "All" "Kepler Maxwell Kepler+Tegra Maxwell+Tegra Pascal" "3.0 7.5")
+  enable_language(CUDA)
+  find_package(CUDAToolkit REQUIRED)
+  if(CMAKE_CUDA_COMPILER_VERSION VERSION_LESS "9.0")
+    message(STATUS "Unsupported CUDA version, please upgrade to CUDA 9+. Disabling CUDA support")
+    set(ENABLE_CUDA "FALSE" CACHE BOOL "Enable CUDA support" FORCE)
+  else()
     find_package(CUDA REQUIRED)
-    if(CUDA_VERSION VERSION_LESS "9.0")
-      message(STATUS "Unsupported CUDA version, please upgrade to CUDA 9+. Disabling CUDA support")
-      set(ENABLE_CUDA "FALSE" CACHE BOOL "Enable CUDA support" FORCE)
-    else()
-      cuda_select_nvcc_arch_flags(CUDA_ARCH_FLAGS ${CUDA_ARCHITECTURES})
-      message(STATUS "Building with CUDA flags: " "${CUDA_ARCH_FLAGS}")
-      if (NOT "arch=compute_70,code=sm_70" IN_LIST CUDA_ARCH_FLAGS)
-        set(ENABLE_CUDNN_HALF "FALSE" CACHE BOOL "Enable CUDNN Half precision" FORCE)
-        message(STATUS "Your setup does not supports half precision (it requires CC >= 7.5)")
-      endif()
+    cuda_select_nvcc_arch_flags(CUDA_ARCH_FLAGS ${CUDA_ARCHITECTURES})
+    message(STATUS "Building with CUDA flags: " "${CUDA_ARCH_FLAGS}")
+    if (NOT "arch=compute_70,code=sm_70" IN_LIST CUDA_ARCH_FLAGS)
+      set(ENABLE_CUDNN_HALF "FALSE" CACHE BOOL "Enable CUDNN Half precision" FORCE)
+      message(STATUS "Your setup does not supports half precision (it requires CC >= 7.5)")
     endif()
-  else()
-    set(ENABLE_CUDA "FALSE" CACHE BOOL "Enable CUDA support" FORCE)
   endif()
+else()
+  set(ENABLE_CUDA "FALSE" CACHE BOOL "Enable CUDA support" FORCE)
 endif()
 
 if (WIN32 AND ENABLE_CUDA AND CMAKE_MAKE_PROGRAM MATCHES "ninja")