dlib: migrate from homebrew/science

Closes #16762.

Signed-off-by: FX Coudert <fxcoudert@gmail.com>

Formula/dlib.rb

@@ -0,0 +1,52 @@
+class Dlib < Formula
+  desc "C++ library for machine learning"
+  homepage "http://dlib.net/"
+  url "http://dlib.net/files/dlib-19.4.tar.bz2"
+  sha256 "003f0508fe605cf397ad678c6976e5ec7db8472faabf06508d16ead205571372"
+  revision 1
+  head "https://github.com/davisking/dlib.git"
+
+  depends_on :macos => :el_capitan # needs thread-local storage
+
+  depends_on "cmake" => :build
+  depends_on "jpeg"
+  depends_on "libpng"
+  depends_on "openblas" => :optional
+  depends_on :x11 => :optional
+
+  needs :cxx11
+
+  def install
+    ENV.cxx11
+
+    args = std_cmake_args + %w[-DDLIB_USE_BLAS=ON -DDLIB_USE_LAPACK=ON]
+    args << "-DDLIB_NO_GUI_SUPPORT=ON" if build.without? "x11"
+
+    if build.with? "openblas"
+      args << "-Dcblas_lib=#{Formula["openblas"].opt_lib}/libopenblas.dylib"
+      args << "-Dlapack_lib=#{Formula["openblas"].opt_lib}/libopenblas.dylib"
+    else
+      args << "-Dcblas_lib=/usr/lib/libcblas.dylib"
+      args << "-Dlapack_lib=/usr/lib/liblapack.dylib"
+    end
+
+    mkdir "dlib/build" do
+      system "cmake", "..", *args
+      system "make", "install"
+    end
+  end
+
+  test do
+    (testpath/"test.cpp").write <<-EOS.undent
+      #include <dlib/logger.h>
+      dlib::logger dlog("example");
+      int main() {
+        dlog.set_level(dlib::LALL);
+        dlog << dlib::LINFO << "The answer is " << 42;
+      }
+    EOS
+    system ENV.cxx, "-std=c++11", "test.cpp", "-o", "test", "-I#{include}",
+                    "-L#{lib}", "-ldlib"
+    assert_match /INFO.*example: The answer is 42/, shell_output("./test")
+  end
+end