openexr: backport gcc-13 fix
Without the change `openexr` build on `gcc-13` fails as:
[ 99%] Building CXX object src/test/OpenEXRTest/CMakeFiles/OpenEXRTest.dir/testInputPart.cpp.o
openexr/src/bin/exrcheck/main.cpp: In function 'bool exrCheck(const char*, bool, bool, bool, bool)':
openexr/src/bin/exrcheck/main.cpp:65:15: error: 'uintptr_t' does not name a type
65 | const uintptr_t kMaxSize = uintptr_t (-1) / 4;
| ^~~~~~~~~