configure.ac, lib/Makefile.am: Respect $(bindir) in PASSWD_PROGRAM

[alejandro-colomar]

Suggested-by: @Karlson2k

---

• This is a subset of configure.ac, src/Makefile.am: Follow GNU coding standards regarding directory variables #1231 at v5b.

Hopefully, this smaller PR will pass the test suite.

---

Revisions:

v2

• Use $bindir instead of $sbindir for passwd(1).

$ git rd 
1:  a884b9bd5 ! 1:  800be64d6 configure.ac, lib/Makefile.am: Respect $(sbindir) in PASSWD_PROGRAM
    @@ Metadata
     Author: Alejandro Colomar <alx@kernel.org>
     
      ## Commit message ##
    -    configure.ac, lib/Makefile.am: Respect $(sbindir) in PASSWD_PROGRAM
    +    configure.ac, lib/Makefile.am: Respect $(bindir) in PASSWD_PROGRAM
     
         Suggested-by: Evgeny Grin (Karlson2k) <k2k@drgrin.dev>
         Signed-off-by: Alejandro Colomar <alx@kernel.org>
    @@ lib/Makefile.am
      
     -DEFS =
     +DEFS = \
    -+  -DPASSWD_PROGRAM='"$(sbindir)/passwd"'
    ++  -DPASSWD_PROGRAM='"$(bindir)/passwd"'
      
      noinst_LTLIBRARIES = libshadow.la
      

v3

• Rename PASSWD_PROGRAM => PATH_PASSWD, for consistency with <paths.h>.

$ git rd 
1:  800be64d6 = 1:  800be64d6 configure.ac, lib/Makefile.am: Respect $(bindir) in PASSWD_PROGRAM
-:  --------- > 2:  90e6a4840 lib/: Rename PASSWD_PROGRAM => PATH_PASSWD