Fix ICU detection in System.Globalization.Native build (dotnet/coreclr#9990)

Fix ICU detection in System.Globalization.Native build (dotnet/coreclr#9990)

The config.cmake was not getting the ICU library paths it requires to
build a code that detects presence of the ucol_setMaxVariable.
I have excluded the libraries detection from the CMakeLists.txt
some time ago since they are not used in the build itself anymore,
but I have not realized that they are needed for this detection
script that's included from the CMakeLists.txt.

Commit migrated from https://github.com/dotnet/coreclr/commit/dc22420af24474fc500cbb47d289337b1762b23d