When building NCCL from source, do not rely on CUDA_TOOLKIT_PATH being defined to find bin2c.

PiperOrigin-RevId: 219698198

third_party/nccl/build_defs.bzl.tpl

@@ -182,8 +182,9 @@ def device_link(name, srcs):
     # Generate fatbin header from all cubins.
     fatbin_hdr = name + ".fatbin.h"
     fatbinary = "@local_config_nccl//:cuda/bin/fatbinary"
-    cmd = ("PATH=$$CUDA_TOOLKIT_PATH/bin:$$PATH " +  # for bin2c
-           "$(location %s) -64 --cmdline=--compile-only --link " % fatbinary +
+    bin2c = "@local_config_nccl//:cuda/bin/bin2c"
+    cmd = ("$(location %s) -64 --cmdline=--compile-only " % fatbinary +
+           "--link --bin2c-path $$(dirname $(location %s)) " % bin2c +
            "--compress-all %s --create=%%{name}.fatbin " % " ".join(images) +
            "--embedded-fatbin=$@")
     native.genrule(
@@ -191,7 +192,7 @@ def device_link(name, srcs):
         outs = [fatbin_hdr],
         srcs = cubins,
         cmd = cmd,
-        tools = [fatbinary],
+        tools = [fatbinary, bin2c],
     )
 
     # Generate the source file #including the headers generated above.

third_party/nccl/nccl_configure.bzl

@@ -3,7 +3,7 @@
 
 `nccl_configure` depends on the following environment variables:
 
-  * `TF_NCCL_VERSION`: The NCCL version.
+  * `TF_NCCL_VERSION`: Installed NCCL version or empty to build from source.
   * `NCCL_INSTALL_PATH`: The installation path of the NCCL library.
   * `NCCL_HDR_PATH`: The installation path of the NCCL header files.
 """
@@ -44,6 +44,7 @@ _NCCL_ARCHIVE_BUILD_CONTENT = """
 exports_files([
     "cuda/bin/crt/link.stub",
     "cuda/bin/fatbinary",
+    "cuda/bin/bin2c",
     "nvlink",
 ])