Fix build with OpenEXR>=3

Index: cmake/modules/FindIlmBase.cmake
--- cmake/modules/FindIlmBase.cmake.orig
+++ cmake/modules/FindIlmBase.cmake
@@ -4,7 +4,7 @@
 
 find_package(PkgConfig QUIET)
 if(PKG_CONFIG_FOUND)
-  pkg_check_modules(PC_ILMBASE QUIET IlmBase)
+  pkg_check_modules(PC_ILMBASE QUIET Imath)
 endif()
 
 if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
@@ -49,11 +49,7 @@ if(IlmBase_INCLUDE_DIR AND EXISTS "${IlmBase_INCLUDE_D
     endif()
 endif()
 
-if("${IlmBase_VERSION}" VERSION_LESS "2.0.0")
-  set(IlmBase_ALL_LIBRARIES Imath Half Iex IlmThread)
-else()
-  set(IlmBase_ALL_LIBRARIES Imath Half Iex IexMath IlmThread)
-endif()
+set(IlmBase_ALL_LIBRARIES Imath Iex IlmThread)
 foreach(ILMBASE_LIB ${IlmBase_ALL_LIBRARIES})
   string(TOUPPER ${ILMBASE_LIB} _upper_ilmbase_lib)
   find_library(IlmBase_${_upper_ilmbase_lib}_LIBRARY