graphics/openxr: fix build on powerpc

/wrkdirs/usr/ports/graphics/openxr/work/OpenXR-SDK-release-1.1.38/src/common/platform_utils.hpp:75:2: error: "No architecture string known!"
   75 | #error "No architecture string known!"
      |  ^

graphics/openxr/files/patch-src_common_platform__utils.hpp

+--- src/common/platform_utils.hpp.orig	2024-07-29 12:32:33 UTC
++++ src/common/platform_utils.hpp
+@@ -55,6 +55,8 @@
+ #define XR_ARCH_ABI "mips"
+ #elif defined(__powerpc64__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+ #define XR_ARCH_ABI "ppc64"
++#elif defined(__powerpc__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
++#define XR_ARCH_ABI "ppc"
+ #elif defined(__powerpc__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ #define XR_ARCH_ABI "ppc64el"
+ #elif defined(__s390x__) || defined(__zarch__)