[llvm] Create a CharSetConverter class with both iconv and icu support (PR #74516)

[Hubert Tong via llvm-commits]

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@@ -257,6 +257,37 @@ else()
   set(LLVM_ENABLE_TERMINFO 0)
 endif()
 
+# Check for ICU.
+if(LLVM_ENABLE_ICU)
+  set(LIBRARY_SUFFIXES ${CMAKE_FIND_LIBRARY_SUFFIXES})
+  set(CMAKE_FIND_LIBRARY_SUFFIXES ".so")
+  if (LLVM_ENABLE_ICU STREQUAL FORCE_ON)
+    find_package(ICU REQUIRED COMPONENTS uc i18n)
+    if (NOT ICU_FOUND)
+      message(FATAL_ERROR "Failed to configure icu, but LLVM_ENABLE_ICU is FORCE_ON")
----------------
hubert-reinterpretcast wrote:

Minor nit. Sorry for missing this before.
```suggestion
      message(FATAL_ERROR "Failed to configure ICU, but LLVM_ENABLE_ICU is FORCE_ON")
```

https://github.com/llvm/llvm-project/pull/74516