fix regression introduced by changeset: 1431:28e9d479aa65 [Use '-p' command line option when running matiec (iec2c)]

Variable matiec_flags in c_ext.py and PythonFileCTNMixin.py is not
used for flags for matiec (IEC to C compiler) actually, but it's used
to compile C-code generated for extensions using normal C-compiler,
like gcc.

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[TOPOLOGY]

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NetName=None

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Nodes=0x01

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Node64Present=0x01

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Node64Name=micromod

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Node64DCFName=PEAK MicroMod.eds

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EDSBaseName=eds