Add package opencascade (#13938)

* Add new package : opencascade

* Remove boilerplate comment

* Fix flake8 errors

* Explicitly disable 3rd parties

var/spack/repos/builtin/packages/opencascade/package.py

+# Copyright 2013-2019 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from spack import *
+
+
+class Opencascade(CMakePackage):
+    """Open CASCADE Technology is a software development kit (SDK)
+    intended for development of applications dealing with 3D CAD data,
+    freely available in open source. It includes a set of C++ class
+    libraries providing services for 3D surface and solid modeling,
+    visualization, data exchange and rapid application development."""
+
+    homepage = "https://www.opencascade.com"
+    url      = "http://git.dev.opencascade.org/gitweb/?p=occt.git;a=snapshot;h=refs/tags/V7_4_0;sf=tgz"
+
+    version('7.4.0', extension='tar.gz',
+            sha256='655da7717dac3460a22a6a7ee68860c1da56da2fec9c380d8ac0ac0349d67676')
+
+    variant('tbb', default=False,
+            description='Build with Intel Threading Building Blocks')
+    variant('vtk', default=False,
+            description='Enable VTK support')
+    variant('freeimage', default=False,
+            description='Build with FreeImage')
+    variant('rapidjson', default=False,
+            description='Build with rapidjson')
+
+    depends_on('intel-tbb', when='+tbb')
+    depends_on('vtk', when='+vtk')
+    depends_on('freeimage', when='+freeimage')
+    depends_on('rapidjson', when='+rapidjson')
+
+    def cmake_args(self):
+        args = []
+
+        if '+tbb' in self.spec:
+            args.append('-DUSE_TBB=ON')
+            args.append('-D3RDPARTY_VTK_DIR=%s' %
+                        self.spec['intel-tbb'].prefix)
+        else:
+            args.append('-DUSE_TBB=OFF')
+
+        if '+vtk' in self.spec:
+            args.append('-DUSE_VTK=ON')
+            args.append('-D3RDPARTY_VTK_DIR=%s' %
+                        self.spec['vtk'].prefix)
+        else:
+            args.append('-DUSE_VTK=OFF')
+
+        if '+freeimage' in self.spec:
+            args.append('-DUSE_FREEIMAGE=ON')
+            args.append('-D3RDPARTY_FREEIMAGE_DIR=%s' %
+                        self.spec['freeimage'].prefix)
+        else:
+            args.append('-DUSE_FREEIMAGE=OFF')
+
+        if '+rapidjson' in self.spec:
+            args.append('-DUSE_RAPIDJSON=ON')
+            args.append('-D3RDPARTY_RAPIDJSON_DIR=%s' %
+                        self.spec['rapidjson'].prefix)
+        else:
+            args.append('-DUSE_RAPIDJSON=OFF')
+
+        return args