Variety of improvements

- Rename sources to distfiles for clarity.
- Per sys(a/c) distfiles to reduce rootfs.py processing and reduce RAM
  usage in sysa.
- Canonicalise early kaem mes/tcc files to kaem script conventions.
- Cleanup unused setup in python.

sysc/run.sh

@@ -15,6 +15,7 @@ export PATH=/usr/bin:/usr/sbin
 export PREFIX=/usr
 export SOURCES=/usr/src
 export DESTDIR=/tmp/destdir
+export DISTFILES=/distfiles
 
 create_fhs() {
     # Add the rest of the FHS that we will use and is not created pre-boot
@@ -36,4 +37,4 @@ create_fhs
 
 build bash-5.1
 
-exec env -i PATH=${PATH} PREFIX=${PREFIX} SOURCES=${SOURCES} DESTDIR=${DESTDIR} bash run2.sh
+exec env -i PATH=${PATH} PREFIX=${PREFIX} SOURCES=${SOURCES} DESTDIR=${DESTDIR} DISTFILES=${DISTFILES} bash run2.sh