Re: Use "$(MKDIR_P) sys", not race-prone "test -d sys || mkdir sys".

[Bruno Haible]

Jim Meyering wrote:
> I wonder which use case made it so using AC_SUBST wasn't an option.

IIRC, it is when the user specifies
  ../path/configure --srcdir=../path
with a relative pathname. Normally you can omit --srcdir, because configure
finds it by itself; then $ac_srcdir is an absolute path; then $(install_sh)
is an absolute path as well.

Such a usage is rare.

Bruno