ports/icu/portfile.cmake only works on Windows. I've identified the following issues that impact Linux:

• MSYS is not needed on Linux
• The zip file, when extracted, uses CRLF line endings, which interferes with bash running runConfigureICU
• The runConfigureICU options MSYS/MSVC and --host=i686-pc-mingw32 are Windows-specific
• Most of the CFLAGS and LDFLAGS are MSVC-specific
• Renaming static libraries to remove the "s" prefix is only necessary on Windows