cmake: build with system curl, zlib, and bzip2

Using the system's curl gives us access to an ssl-enabled curl library,
which is important as CMake will not be able to download assets from
GitHub and other sites that host them via https without ssl support.  An
alternative, would be to build with "-- -DCMAKE_USE_OPENSSL=ON" instead,
as CMake doesn't enable ssl support by default with its bundled libcurl.

Also, enable the system zlib and bzip2 at the recommendation of
@mikemcquaid.

Closes Homebrew/homebrew#38147.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Formula/cmake.rb

@@ -66,6 +66,9 @@ class Cmake < Formula
       --datadir=/share/cmake
       --docdir=/share/doc/cmake
       --mandir=/share/man
+      --system-curl
+      --system-zlib
+      --system-bzip2
     ]
 
     if build.with? "docs"