[scudo][standalone] Correct cmake copy/paste error

[cryptoad]

Summary

I mistakenly used a SCUDO variable instead of SCUDO_STANDALONE one. The net
result was that there were more architecture supported than I intended.
Correct that, I'll add more architectures once the bots are enabled and
green for x86.

cmake/config-ix.cmake

else()
   filter_available_targets(PROFILE_SUPPORTED_ARCH ${ALL_PROFILE_SUPPORTED_ARCH})
   filter_available_targets(TSAN_SUPPORTED_ARCH ${ALL_TSAN_SUPPORTED_ARCH})
   filter_available_targets(UBSAN_SUPPORTED_ARCH ${ALL_UBSAN_SUPPORTED_ARCH})
   filter_available_targets(SAFESTACK_SUPPORTED_ARCH
     ${ALL_SAFESTACK_SUPPORTED_ARCH})
   filter_available_targets(CFI_SUPPORTED_ARCH ${ALL_CFI_SUPPORTED_ARCH})
   filter_available_targets(ESAN_SUPPORTED_ARCH ${ALL_ESAN_SUPPORTED_ARCH})
   filter_available_targets(SCUDO_SUPPORTED_ARCH ${ALL_SCUDO_SUPPORTED_ARCH})
-  filter_available_targets(SCUDO_STANDALONE_SUPPORTED_ARCH ${ALL_SCUDO_SUPPORTED_ARCH})
+  filter_available_targets(SCUDO_STANDALONE_SUPPORTED_ARCH ${ALL_SCUDO_STANDALONE_SUPPORTED_ARCH})
   filter_available_targets(XRAY_SUPPORTED_ARCH ${ALL_XRAY_SUPPORTED_ARCH})
   filter_available_targets(SHADOWCALLSTACK_SUPPORTED_ARCH
     ${ALL_SHADOWCALLSTACK_SUPPORTED_ARCH})
 endif()
 
 if (MSVC)
   # See if the DIA SDK is available and usable.
   set(MSVC_DIA_SDK_DIR "$ENV{VSINSTALLDIR}DIA SDK")