[llvm] [SPIRV] Add option to add all KHR extensions (PR #145535)

[Nathan Gauër via llvm-commits]

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@@ -119,6 +119,13 @@ bool SPIRVExtensionsParser::parse(cl::Option &O, StringRef ArgName,
       continue;
     }
 
+    if (Token == "KHR") {
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Keenuts wrote:

is the token normalized to upper? Shall we accept both `KHR` and `khr`?

https://github.com/llvm/llvm-project/pull/145535