remove openmp-simd flag on older compilers

This will slow down denoising when built on an older machine, but
no worse than it was before oidn v1.2.0.

projects/openimagedenoise.cmake

@@ -5,3 +5,6 @@ superbuild_add_project(openimagedenoise
     -DCMAKE_INSTALL_NAME_DIR:PATH=<INSTALL_DIR>/lib
     -DCMAKE_INSTALL_LIBDIR:STRING=lib
 )
+
+superbuild_apply_patch(openimagedenoise fix-openmp-flag
+  "Fix openmp-simd flag on older compilers")

projects/patches/openimagedenoise-fix-openmp-flag.patch

+diff --git a/cmake/oidn_platform.cmake b/cmake/oidn_platform.cmake
+index b06853e..a292c2f 100644
+--- a/cmake/oidn_platform.cmake
++++ b/cmake/oidn_platform.cmake
+@@ -1,6 +1,8 @@
+ ## Copyright 2009-2020 Intel Corporation
+ ## SPDX-License-Identifier: Apache-2.0
+ 
++include(CheckCXXCompilerFlag)
++
+ set(OIDN_C_CXX_FLAGS)
+ set(OIDN_C_CXX_FLAGS_RELEASE)
+ set(OIDN_C_CXX_FLAGS_DEBUG)
+@@ -142,7 +144,10 @@ if(WIN32)
+ elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
+   append(OIDN_C_CXX_FLAGS "-qopenmp-simd")
+ else()
+-  append(OIDN_C_CXX_FLAGS "-fopenmp-simd")
++  check_cxx_compiler_flag(-fopenmp-simd compiler-openmp-simd-support)
++  if(compiler-openmp-simd-support)
++    append(OIDN_C_CXX_FLAGS "-fopenmp-simd")
++  endif()
+ endif()
+ 
+ ## -----------------------------------------------------------------------------