[llvm] [cmake] Sync Haiku cases in config.guess with downstream (PR #228784)

[Brad Smith via llvm-commits]

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@@ -1256,8 +1256,11 @@ EOF
     BePC:Haiku:*:*)	# Haiku running on Intel PC compatible.
 	echo i586-pc-haiku
 	exit ;;
-    x86_64:Haiku:*:*) # Haiku running on x86_64.
-	echo x86_64-unknown-haiku
+    ppc:Haiku:*:*)	# Haiku running on Apple PowerPC
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brad0 wrote:

Ya, downstream added it a few years ago. I figured no big deal to keep it in sync.

https://github.com/llvm/llvm-project/pull/228784