Fix build on sparc64 by not erroring out

Index: hwy/detect_compiler_arch.h
--- hwy/detect_compiler_arch.h.orig
+++ hwy/detect_compiler_arch.h
@@ -441,8 +441,6 @@
 #define HWY_ARCH_MAX_BYTES 32
 #elif HWY_ARCH_PPC || HWY_ARCH_S390X || HWY_ARCH_ARM_V7 || HWY_ARCH_ARM_OLD
 #define HWY_ARCH_MAX_BYTES 16
-#else
-#error "Missing case for HWY_ARCH_*"
 #endif
 
 //------------------------------------------------------------------------------
