new package: protobuf-c (#12634)

* new package: protobuf-c

* Update var/spack/repos/builtin/packages/protobuf-c/package.py

Co-Authored-By: Adam J. Stewart <ajstewart426@gmail.com>

var/spack/repos/builtin/packages/protobuf-c/package.py

@@ -0,0 +1,20 @@
+# 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 ProtobufC(AutotoolsPackage):
+    """
+    Protocol Buffers implementation in C
+    """
+
+    homepage = "https://github.com/protobuf-c/protobuf-c"
+    url      = "https://github.com/protobuf-c/protobuf-c/releases/download/v1.3.2/protobuf-c-1.3.2.tar.gz"
+
+    version('1.3.2', sha256='53f251f14c597bdb087aecf0b63630f434d73f5a10fc1ac545073597535b9e74')
+
+    depends_on('protobuf')
+    depends_on('pkgconfig', type='build')