Improve aliBuild clean (#306)

- Now supports the --aggressive-cleanup option, which can be used
  to remove extra files which come handy only in case of rebuilds.
  This means that in general the cleanup has no side effects, but
  it will take longer to rebuild a package.
- Do not remove files which do not exists.

aliBuild

@@ -482,13 +482,19 @@ def doMain():
     symlinksBuild = [readlink(x) for x in glob("%s/BUILD/*-latest*" % args.workDir)]
     # $WORK_DIR/TMP should always be cleaned up. This does not happen only
     # in the case we run out of space while unpacking.
+    # $WORK_DIR/<architecture>/store can be cleaned up as well, because
+    # we do not need the actual tarballs after they have been built.
     toDelete = ["%s/TMP" % args.workDir]
+    if args.aggressiveCleanup:
+      toDelete += ["%s/TARS/%s/store" % (args.workDir, args.architecture),
+                   "%s/SOURCES" % (args.workDir)]
     toDelete += [x for x in glob("%s/BUILD/*" % args.workDir)
                  if not islink(x) and not basename(x) in symlinksBuild]
     installGlob ="%s/%s/*/" % (args.workDir, args.architecture)
     symlinksInstall = [readlink(x) for x in glob(installGlob + "latest*")]
     toDelete += [x for x in glob(installGlob+ "*")
                  if not islink(x) and not basename(x) in symlinksInstall]
+    toDelete = [x for x in toDelete if exists(x)]
     if not toDelete:
       print "Nothing to delete."
       exit(0)