BaseTools Script: Update ConvertFceToStructurePcd to report warning messages
BaseTools Script: Update ConvertFceToStructurePcd to report warning messages

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1297
When the header files are not found for the used C structure, this script will
report the warning, let user know there is no header file to define C structure.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Wang BinX A <4368bbf252479ab5aa0160effa6a700cf82ac152@intel.com>
Reviewed-by: Liming Gao <6480311aeeb4b006862f6d13ebabddc03f51e507@intel.com>

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