[Povray] Work around build failure due to target OS macros changes.

llvm/llvm-project#74676 changes some predefined
target OS macros on Apple platforms, which breaks building both Blender
and Povray.

Work around build failures by adding -fno-define-target-os-macros if
available.

(Workaround has already been applied to SPEC2017's version of Povray in
9b14a92)

Author: fhahn

External/Povray/CMakeLists.txt

@@ -12,6 +12,19 @@ if(TEST_SUITE_POVRAY_ROOT)
     ${TEST_SUITE_POVRAY_ROOT}/source/libpng/example.c
   )
 
+if(APPLE)
+  # Building Povray breaks with -fdefine-target-os-macros, add flag to disable
+  # it as workaround.
+  include(CheckCCompilerFlag)
+  check_c_compiler_flag(-fno-define-target-os-macros
+                        COMPILER_HAS_NO_DEFINE_TARGET_OS_MACROS)
+  if (COMPILER_HAS_NO_DEFINE_TARGET_OS_MACROS)
+	list(APPEND CPPFLAGS
+      -fno-define-target-os-macros
+    )
+  endif()
+endif()
+
   list(APPEND CPPFLAGS
     -I${TEST_SUITE_POVRAY_ROOT}/source
     -I${TEST_SUITE_POVRAY_ROOT}/source/unix

External/SPEC/CFP2006/453.povray/CMakeLists.txt

@@ -9,6 +9,17 @@ if(ARCH STREQUAL "AArch64" OR ARCH STREQUAL "LoongArch")
   list(APPEND CXXFLAGS -ffp-contract=off)
 endif()
 
+if(APPLE)
+  # Building Povray breaks with -fdefine-target-os-macros, add flag to disable
+  # it as workaround.
+  include(CheckCCompilerFlag)
+  check_c_compiler_flag(-fno-define-target-os-macros
+                        COMPILER_HAS_NO_DEFINE_TARGET_OS_MACROS)
+  if (COMPILER_HAS_NO_DEFINE_TARGET_OS_MACROS)
+    add_compile_options(-fno-define-target-os-macros)
+  endif()
+endif()
+
 macro(test_input run_type stdout_reltol)
   llvm_test_run(RUN_TYPE ${run_type}
     WORKDIR %S/data/${run_type}/input