Added optimized version of Blis for AMD (#14780)

The Blis package has been refactored to be able to
reuse the build logic for the fork of the project
optimized for AMD.

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

@@ -0,0 +1,22 @@
+# Copyright 2013-2020 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.pkg.builtin.blis import BlisBase
+
+
+class Amdblis(BlisBase):
+    """AMD Optimized BLIS.
+
+    BLIS is a portable software framework for instantiating high-performance
+    BLAS-like dense linear algebra libraries. The framework was designed to
+    isolate essential kernels of computation that, when optimized, immediately
+    enable optimized implementations of most of its commonly used and
+    computationally intensive operations.
+    """
+
+    homepage = "https://developer.amd.com/amd-aocl/blas-library/"
+    url = "https://github.com/amd/blis/archive/2.1.tar.gz"
+    git = "https://github.com/amd/blis.git"
+
+    version('2.1', sha256='3b1d611d46f0f13b3c0917e27012e0f789b23dbefdddcf877b20327552d72fb3')