plugin/core: autotools: make awk crlf agnostic when generating ps.h

plugin/core: autotools: make awk crlf agnostic when generating ps.h

Fixes errors like this with Cygwin in a crlf environment even with
SHELLOPTS=igncr:

ps.h:2:1: error: missing terminating " character
    2 | "%%BeginProlog ",
      | ^~~~~~~~~~~~~~

Although not shown in the error message, this line actually contained
a carriage return after %%BeginProlog:

"%%BeginProlog\r",