image: fix device profile specific COMPILE targets

image: fix device profile specific COMPILE targets

Commit a01d23e75 ("image: always rebuild kernel loaders")
is a step in the right direction, but exposed some issues
and regressions in the makefile.

Some of the files made by device specific COMPILE targets
start with an "append" command (i.e. >> instead of > redirection)
and if the file already exists, the target file is the
input to itself before the first recipe-specified input.

Fixes: a01d23e75 ("image: always rebuild kernel loaders")
Fixes: a7fb589e8 ("image: always rebuild kernel loaders")
Signed-off-by: Michael Pratt <mcpratt@pm.me>