ecpg leaves broken files around

When working on the ecpg regression stuff things, it's the first time
I've actually used ecpg. And I notice now that it leaves incomplete and
broken files around when it fails. For example, I currently get:
parser.pgc:26: ERROR: syntax error at or near "NULLS"

when building. I have to investigate why later, but when I run ecpg on
this it leaves a parser.c file around, which the build system on the
next run picks up as there and doesn't try to rebuild. Naturally, it
fails later when the C compiler tries to build this file.

AFAIK, most other compilers delete their output if it's not valid. Is
there any particular reason why ecpg doesn't do this?

//Magnus