[clang] [Clang][Driver] Skip empty strings in getAArch64MultilibFlags (PR #97827)

[Peter Smith via cfe-commits]

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@@ -0,0 +1,4 @@
+// RUN: %clang --target=aarch64-none-elf -march=armv8.9-a+rcpc3 -print-multi-flags-experimental -c %s 2>&1 | FileCheck %s
+
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smithp35 wrote:

I think it could be worth a comment here explaining what the test is checking for as it would likely need git blame to work it out otherwise. For example:
```
// rcpc3 implies rcpc-immo which does not have a user-visible name, check that an empty string is not produced.
```

https://github.com/llvm/llvm-project/pull/97827