pybind11 1.8.1 (new formula)

Closes #4059.

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

Formula/pybind11.rb

@@ -0,0 +1,39 @@
+class Pybind11 < Formula
+  desc "Seamless operability between C++11 and Python"
+  homepage "https://github.com/pybind/pybind11"
+  url "https://github.com/pybind/pybind11/archive/v1.8.1.tar.gz"
+  sha256 "321de8881ff0e113087b9e996d77777417b7db05bc4536b365f648b5fadc27b8"
+
+  depends_on "python3"
+  depends_on "cmake" => :build
+
+  def install
+    system "cmake", ".", *std_cmake_args
+    system "make", "install"
+  end
+
+  test do
+    (testpath/"example.cpp").write <<-EOS.undent
+      #include <pybind11/pybind11.h>
+
+      int add(int i, int j) {
+          return i + j;
+      }
+      namespace py = pybind11;
+      PYBIND11_PLUGIN(example) {
+          py::module m("example", "pybind11 example plugin");
+          m.def("add", &add, "A function which adds two numbers");
+          return m.ptr();
+      }
+    EOS
+
+    (testpath/"example.py").write <<-EOS.undent
+      import example
+      example.add(1,2)
+    EOS
+
+    python_flags = `python3-config --cflags --ldflags`.split(" ")
+    system ENV.cxx, "-O3", "-shared", "-std=c++11", *python_flags, "example.cpp", "-o", "example.so"
+    system "python3", "example.py"
+  end
+end