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.

from ..toolchain_gcc import toolchain_gcc

class Linux_target(toolchain_gcc):
    dlopen_prefix = "./"
    extension = ".so"
    def getBuilderCFLAGS(self):
        return toolchain_gcc.getBuilderCFLAGS(self) + ["-fPIC"]
    def getBuilderLDFLAGS(self):
        return toolchain_gcc.getBuilderLDFLAGS(self) + ["-shared", "-lrt"]