stagefiles: further robustify with auto filenames

as suggested by Raphaël

rather than have fixed stagefile filename strings at all in the scripts,
use `$(basename $0)` to use the name of the script (which is the same for
almost all cases anyway, and the stage files are supposed to be almost
exclusively unique per-script). we can thus simplify things by determining
the filename for most use cases within the functions themselves.

this does change the file used by a couple of scripts, affecting backwards
compatibility of executing live-build upon an existing partially or fully
completed build:
 - binary_grub-pc used "binary_grub"
 - chroot_includes used "includes.chroot"

care had to be taken for the following cases:
 - there are some cases like bootstrap_cache, source_debian and
   bootstrap_debootstrap which are dealing with more than one file, and/or
   otherwise a filename that is not specific to the script itself exactly,
   or should not be based upon its name.
 - some cases like chroot_cache, bootstrap_cache and
   chroot_install-packages need to append something to the end of the name
   depending upon which pass/action mode the script is being executed with.
 - furthermore in the bootstrap_cache case one of the filenames is used
   within the bootstrap_debootstrap and thus needs very careful handling
   to be certain that a change in filename of bootstrap_cache does not
   break bootstrap_debootstrap.

Gbp-Dch: Short

1 files changed, 1 insertions, 1 deletions

diff --git a/scripts/build/config b/scripts/build/config
index a344c59e6..e2d8f13f9 100755
--- a/scripts/build/config
+++ b/scripts/build/config
@@ -1513,4 +1513,4 @@ Type: ${LIVE_IMAGE_TYPE}
 EOF
 
 # Creating stage file
-Create_stagefile config
+Create_stagefile