Change cinst from stdin input to use arguments. As we have to execute this process on Windows over the shell a stdin / stdout communication is not really possible without some major hacks. So you now have to supply an instructions file and the path to the certificatelist as arguments when this process is called

# - Try to find PolarSSL

# Find the include directories
find_path(POLARSSL_INCLUDE_DIR NAMES polarssl/ssl.h)

find_library(POLARSSL_LIBRARIES NAMES polarssl)

include(FindPackageHandleStandardArgs)

find_package_handle_standard_args(POLARSSL
    REQUIRED_VARS POLARSSL_INCLUDE_DIR POLARSSL_LIBRARIES
)