Build not aborted if LDAP support explicitly requested but can't be enabled

[jzakrzewski]

I did:
./configure --prefix=/usr/local/curl/ --enable-ldap --with-ldap-lib --with-lber-lib

I expected:
Aborted build because there are no LDAP libraries/headers on this machine

Actual:

configure: Configured to build curl/libcurl:

  Host setup:       x86_64-pc-linux-gnu
  Install prefix:   /usr/local/curl
  Compiler:         gcc
   CFLAGS:          -Werror-implicit-function-declaration -O2 -Wno-system-headers -pthread
   CPPFLAGS:        
   LDFLAGS:         
   LIBS:            

  curl version:     7.76.1
  SSL:              no      (--with-{ssl,gnutls,nss,mbedtls,wolfssl,schannel,secure-transport,mesalink,amissl,bearssl,rustls} )
  SSH:              no      (--with-{libssh,libssh2})
  zlib:             no      (--with-zlib)
  brotli:           no      (--with-brotli)
  zstd:             no      (--with-zstd)
  GSS-API:          no      (--with-gssapi)
  GSASL:            no      (libgsasl not found)
  TLS-SRP:          no      (--enable-tls-srp)
  resolver:         POSIX threaded
  IPv6:             enabled
  Unix sockets:     enabled
  IDN:              no      (--with-{libidn2,winidn})
  Build libcurl:    Shared=yes, Static=yes
  Built-in manual:  no      (--enable-manual)
  --libcurl option: enabled (--disable-libcurl-option)
  Verbose errors:   enabled (--disable-verbose)
  Code coverage:    disabled
  SSPI:             no      (--enable-sspi)
  ca cert bundle:   no
  ca cert path:     
  ca fallback:      
  LDAP:             no      (--enable-ldap / --with-ldap-lib / --with-lber-lib)
  LDAPS:            no      (--enable-ldaps)
  RTSP:             enabled
  RTMP:             no      (--with-librtmp)
  Metalink:         no      (--with-libmetalink)
  PSL:              no      (libpsl not found)
  Alt-svc:          enabled
  HTTP1:            enabled (internal)
  HTTP2:            no      (--with-nghttp2, --with-hyper)
  HTTP3:            no      (--with-ngtcp2, --with-quiche)
  ECH:              no      (--enable-ech)
  Protocols:        DICT FILE FTP GOPHER HTTP IMAP MQTT POP3 RTSP SMTP TELNET TFTP
  Features:         AsynchDNS IPv6 Largefile UnixSockets alt-svc