Update the way we handle directories supplied by the user:
- the tarball directory is considered as a local copy, and tarballs are copied to a working area,
- the sources and build directories (CT_SRC_DIR and CT_BUILD_DIR) are now computed, and no longer an option,
- the build dir has been renamed from 'build' to 'targets'.
That should ease preparing a tarball of the resulting target.

 --- glibc-2.2.5/malloc/tst-calloc.c.old	Sun Aug  3 16:17:58 2003

 +++ glibc-2.2.5/malloc/tst-calloc.c	Sun Aug  3 16:20:01 2003

 @@ -24,9 +24,8 @@

  #include <stdio.h>

 -/* Number of samples per size.  */

 -#define N 50000

 -

 +/* Number of samples per size.  This is also the maximum memory consumption in kilobytes. */

 +#define N 8000

  static void

  fixed_test (int size)