There were two problems with pkg_use_enabled:
1. It did not detect force-enabled or masked USE flags correctly -
selinux USE flag is force-enabled and is shown in the output inside
parentheses.
2. It was defined in board_options.sh which injects some command line
flags and globals that are not related to the function.
Since pkg_use_enabled was only used so far for checking the selinux
USE flags, add a function is_selinux_enabled and use the newly added
function in the currently only user of pkg_use_enabled.
Signed-off-by: Krzesimir Nowak <knowak@microsoft.com>
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