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.

sysa/bzip2-1.0.8/bzip2-1.0.8.sh

@@ -13,7 +13,9 @@ src_compile() {
 }
 
 src_install() {
-    install -D bzip2 ${DESTDIR}${PREFIX}/bin/bzip2
+    # Manually install bzip2 (cannot replace binary while running)
+    install -D bzip2 ${PREFIX}/bin/bzip2
+    mkdir -p ${DESTDIR}${PREFIX}/bin
     ln -sf ${PREFIX}/bin/bzip2 ${DESTDIR}${PREFIX}/bin/bunzip2
     ln -sf ${PREFIX}/bin/bzip2 ${DESTDIR}${PREFIX}/bin/bzcat
 }