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

[Eli Friedman via llvm-commits]

================
@@ -257,6 +257,26 @@ else()
   set(LLVM_ENABLE_TERMINFO 0)
 endif()
 
+#Check for icu.
+if(LLVM_ENABLE_ICU)
+  find_package(ICU COMPONENTS uc i18n)
----------------
efriedma-quic wrote:

https://discourse.llvm.org/t/rfc-enabling-fexec-charset-support-to-llvm-and-clang-reposting/71512/30 distinguishes between statically and dynamically linking against ICU; which one does this do?

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