add additional libraries to check for LDAP support

[aixtools]

A PR to resolve issue-3595.

On AIX additional libraries (-lcrypt and -lssl) must be provided for openldap to link properly

Fixes #3595

[aixtools]

FYI: with this patch I get:
configure: Configured to build curl/libcurl:

  Host setup:       powerpc-ibm-aix5.3.7.0
  Install prefix:   /opt
  Compiler:         xlc_r
   CFLAGS:          -I/opt/include -O2 -qmaxmem=-1 -qarch=pwr5
   CPPFLAGS:        -I/opt/include -qthreaded -qnoansialias -qhalt=e -I/opt/include -I/opt/include
   LDFLAGS:         -L/opt/lib -L/opt/lib
   LIBS:            -lssh2 -lssh2 -lssl -lcrypto -lldap -llber -lssl -lcrypto -lz

  curl version:     7.64.0
  SSL support:      enabled (OpenSSL)
  SSH support:      enabled (libSSH2)
  zlib support:     enabled
  brotli support:   no      (--with-brotli)
  GSS-API support:  no      (--with-gssapi)
  TLS-SRP support:  enabled
  resolver:         POSIX threaded
  IPv6 support:     enabled
  Unix sockets support: enabled
  IDN support:      no      (--with-{libidn2,winidn})
  Build libcurl:    Shared=yes, Static=no
  Built-in manual:  enabled
  --libcurl option: enabled (--disable-libcurl-option)
  Verbose errors:   enabled (--disable-verbose)
  Code coverage:    disabled
  SSPI support:     no      (--enable-sspi)
  ca cert bundle:   /var/ssl/cacert.pem   (warning: certs not found)
  ca cert path:     no
  ca fallback:      no
  LDAP support:     enabled (OpenLDAP)
  LDAPS support:    enabled
  RTSP support:     enabled
  RTMP support:     no      (--with-librtmp)
  metalink support: no      (--with-libmetalink)
  PSL support:      no      (libpsl not found)
  HTTP2 support:    disabled (--with-nghttp2)
  Protocols:        DICT FILE FTP FTPS GOPHER HTTP HTTPS IMAP IMAPS LDAP LDAPS POP3 POP3S RTSP SCP SFTP SMB SMBS SMTP SMTPS TELNET TFTP

[bagder]

I suppose this doesn't hurt to add as we've already gone down that rabbit hole, but generally I don't think it worth pursuing attempts to link with static libs in configure.

[bagder]

LIBS: -lssh2 -lssh2 -lssl -lcrypto -lldap -llber -lssl -lcrypto -lz

So you now got -lssl -lcrypto added twice on the command line! So perhaps the fix could instead have been to prepend the LDAP libraries to the existing LIBS instead of appending them in the loop that tests them?

[jay]

I suppose this doesn't hurt to add as we've already gone down that rabbit hole

Why go deeper and who's to say ssl and crypto will be available

Nevermind I didn't check what was happening, I thought it was going to be required which it's not.

[aixtools]

Prepending them should work, but that would take much more "thinking" on my part. This is pragmatic (or least invasive).

In any case - I hope it helps!

[jay]

Thanks