Adding Intel LLVM compiler (#13618)

* Adding Intel LLVM compiler.

* Fixing some minor issues.

* Split build environment on run environment in intel-llvm.

var/spack/repos/builtin/packages/intel-llvm/package.py

@@ -0,0 +1,50 @@
+# 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 IntelLlvm(CMakePackage):
+    """Intel's version of the LLVM compiler.
+    """
+
+    homepage = 'https://github.com/intel/llvm'
+    git = 'https://github.com/intel/llvm.git'
+
+    family = 'compiler'
+
+    version('sycl', branch='sycl')
+
+    depends_on('cmake@3.4.3:', type='build')
+
+    # It doesn't seem possible to use != in a conflicts statement
+    # conflicts('target != x86_64',
+    #            msg='Intel LLVM compiler currently only works for x86')
+
+    def setup_build_environment(self, env):
+        env.append_flags('CXXFLAGS', self.compiler.cxx11_flag)
+
+    def setup_run_environment(self, env):
+        if '+clang' in self.spec:
+            env.set('CC', join_path(self.spec.prefix.bin, 'clang'))
+            env.set('CXX', join_path(self.spec.prefix.bin, 'clang++'))
+
+    root_cmakelists_dir = 'llvm'
+
+    def cmake_args(self):
+
+        cmake_args = []
+
+        cmake_args.extend([
+            '-DLLVM_TARGETS_TO_BUILD=X86',
+            '-DLLVM_EXTERNAL_PROJECTS=llvm-spirv;sycl',
+            '-DLLVM_ENABLE_PROJECTS=clang;llvm-spirv;sycl',
+            '-DLLVM_EXTERNAL_SYCL_SOURCE_DIR={0}'.format(
+                join_path(self.stage.source_path, 'sycl')),
+            '-DLLVM_EXTERNAL_LLVM_SPIRV_SOURCE_DIR={0}'.format(
+                join_path(self.stage.source_path, 'llvm-spirv')),
+        ])
+
+        return cmake_args