[ci] fix mac build

.github/workflows/main.yml

@@ -516,6 +516,7 @@ jobs:
           brew update
           # brew unlink python@2
           brew bundle --file=tests/Brewfile --no-upgrade || brew link --overwrite awscli
+          brew install libunistring
           brew install cpanminus
           cpanm IPC::System::Simple
           cpanm String::ShellQuote

extra/github-actions/build-mac.yml

@@ -13,6 +13,7 @@
     brew update
     # brew unlink python@2
     brew bundle --file=tests/Brewfile --no-upgrade || brew link --overwrite awscli
+    brew install libunistring
     brew install cpanminus
     cpanm IPC::System::Simple
     cpanm String::ShellQuote