New package: ripgrep (#15343)

Add package for ripgrep:

    ripgrep is a line-oriented search tool that recursively searches
    your current directory for a regex pattern.  ripgrep is similar to
    other popular search tools like The Silver Searcher, ack and grep.

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

+# 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 import *
+
+
+class Ripgrep(Package):
+    """ripgrep is a line-oriented search tool that recursively searches
+    your current directory for a regex pattern.  ripgrep is similar to
+    other popular search tools like The Silver Searcher, ack and grep.
+    """
+
+    homepage = "https://github.com/BurntSushi/ripgrep"
+    url      = "https://github.com/BurntSushi/ripgrep/archive/11.0.2.tar.gz"
+
+    version('11.0.2', sha256='0983861279936ada8bc7a6d5d663d590ad34eb44a44c75c2d6ccd0ab33490055')
+
+    depends_on('rust')
+
+    def install(self, spec, prefix):
+        cargo = which('cargo')
+        cargo('install', '--root', prefix, '--path', '.')
+
+    # needed for onig_sys
+    def setup_build_environment(self, env):
+        env.append_flags('LLVM_CONFIG_PATH',
+                         join_path(self.spec['llvm'].prefix.libexec.llvm,
+                                   'llvm-config'))
+        env.append_flags('LIBCLANG_PATH', self.spec['llvm'].prefix.lib)