[clang] Remove .. from clang resource path when specified with CLANG_RESOURCE_DIR (PR #216996)

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@@ -0,0 +1,9 @@
+// REQUIRES: clang-vendor=SIE
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rgal wrote:

Thanks. Understood. We have used such a configuration for a long time without issue so hopefully it's not likely to be a problem, if it is, then we (SIE) will certainly want to fix it. My hope (based on discourse), is that this configuration could be useful to other vendors.

https://github.com/llvm/llvm-project/pull/216996