Include icuio lib

[LukaHorvat]

This seems to fix issues like haskell/lsp#56 and haskell/lsp#41

[gzh]

Not only this seems to fix those issues. This seems to be the only correct link options on MinGW.

Because cbits/text_icu.c references ucnv_getMaxCharSize, and the latter is exported from libicuio.dll.

$ grep -r ucnv_getMaxCharSize /mingw32/bin
Binary file /mingw32/bin/libicuio62.dll matches
Binary file /mingw32/bin/libicuuc62.dll matches

$ nm /mingw32/bin/libicuio62.dll| grep ucnv_getMaxCharSize
6a391310 I __imp__ucnv_getMaxCharSize_62

$ nm /mingw32/bin/libicuuc62.dll| grep ucnv_getMaxCharSize

$

I can confirm this patch does work. Invented quite the same fix by myself and was going to submit an identical PR, but then discovered this one. I've tested this on MinGW 32-bit (just updated with pacman -Syu), ICU 6.2, GHC 8.4.3.

[daniel-chambers]

I'd love to see this PR merged! 😃 Without this fix, this library causes some builds to fail on Windows. See my experience over at commercialhaskell/stack#4415, where they kindly pointed me to this fix.

[vshabanov]

Could you please test whether the latest sources are building fine on Windows? Many PRs were merged, but I have no Windows machine to test how the library works there.

And please run cabal test to see whether all tests are passing.