nccl-fastsocket: initial packaging for nccl-fastsocket (#36557)

* nccl-fastsocket: Add NCCL transport plugin for GCP
* nccl-fastsocket: remove auto-gen. header and fix maintainers
* Update var/spack/repos/builtin/packages/nccl-fastsocket/package.py
* nccl-fastsocket: Add rationale for setting LD_LIBRARY_PATH

---------

Co-authored-by: Tamara Dahlgren <35777542+tldahlgren@users.noreply.github.com>

var/spack/repos/builtin/packages/nccl-fastsocket/package.py

@@ -0,0 +1,65 @@
+# Copyright 2013-2023 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)
+
+import tempfile
+
+from spack.package import *
+
+
+class NcclFastsocket(Package):
+    """NCCL Fast Socket GCP Net plugin for NCCL"""
+
+    homepage = "https://github.com/google/nccl-fastsocket"
+    git = "https://github.com/google/nccl-fastsocket.git"
+
+    version("master", preferred=True)
+
+    depends_on("bazel", type="build")
+    depends_on("nccl", type=["build", "run"])
+
+    maintainers("danielahlin")
+
+    def setup_build_environment(self, env):
+        spec = self.spec
+        tmp_path = tempfile.mkdtemp(prefix="spack")
+        env.set("TEST_TMPDIR", tmp_path)
+        env.set("NCCL_INSTALL_PATH", spec["nccl"].prefix)
+        env.set("NCCL_HDR_PATH", spec["nccl"].prefix.include)
+
+    def install(self, spec, prefix):
+        tmp_path = env["TEST_TMPDIR"]
+        # Copied of py-tensorflow
+        args = [
+            # Don't allow user or system .bazelrc to override build settings
+            "--nohome_rc",
+            "--nosystem_rc",
+            # Bazel does not work properly on NFS, switch to /tmp
+            "--output_user_root=" + tmp_path,
+            "build",
+            "libnccl-net.so",
+            # Spack logs don't handle colored output well
+            "--color=no",
+            "--jobs={0}".format(make_jobs),
+            # Enable verbose output for failures
+            "--verbose_failures",
+            # Show (formatted) subcommands being executed
+            "--subcommands=pretty_print",
+            # Ask bazel to explain what it's up to
+            # Needs a filename as argument
+            "--explain=explainlogfile.txt",
+            # Increase verbosity of explanation,
+            "--verbose_explanations",
+        ]
+        bazel(*args)
+        install_tree("bazel-bin", prefix.lib)
+
+    def setup_run_environment(self, env):
+        # The current plugin pickup method of NCCL is to scan for libraries with certain
+        # names in the standard library search paths. Consequently, to make nccl-fastsocket
+        # discoverable to NCCL it is necessary to add it to the LD_LIBRARY_PATH.
+        env.prepend_path("LD_LIBRARY_PATH", self.prefix.lib)
+        # NCCL_NET_PLUGIN can be used to change part of the library-name NCCL is looking
+        # for. This is not necessary for this plugin so it is set to the empty string.
+        env.set("NCCL_NET_PLUGIN", "")