[clang] [flang] [llvm] [CMake] Drop per-target LLVM_REQUIRES_RTTI (PR #174201)

[Alexis Engelke via cfe-commits]

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@@ -1,7 +1,10 @@
 # The interpreter can throw an exception from user input. The test binary needs
 # to be compiled with exception support to catch the thrown exception.
+#
+# NOTE: we compile with exceptions enabled, but (possibly) with RTTI disabled.
+# This only works in these limited circumstances where all exception-related
+# code is in the same library/executable.
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aengelke wrote:

Yeah, that's why I retained the LLVM_REQUIRES_EH -- in this test, the catch should compile and work fine without RTTI.

(As a side note, on MSVC, it looks like vtables have a different layout depending on whether RTTI is enabled, so I would expect linking non-RTTI and RTTI code to be at least fragile. But I'm not 100% sure here, I don't use MSVC.)

https://github.com/llvm/llvm-project/pull/174201