[Bazel] link backtrace library when building llvm/lib/Support under FreeBSD

[wamuir]

Summary

Links the backtrace library which is required under FreeBSD when building llvm/lib/Support. This library is similarly linked by CMake on BSD builds at llvm/lib/Support/CMakeLists.txt

[wamuir]

@GMNGeoffrey would you be willing to suggest a reviewer for this revision? Thanks!

[GMNGeoffrey]

LGTM

[wamuir]

Thank you. Can you also land? I recall in the past that authorship information has been required; if so, mine is William Muir <[e-mail]>

utils/bazel/llvm-project-overlay/llvm/BUILD.bazel

]) + [
         "include/llvm/ExecutionEngine/JITSymbol.h",
         "include/llvm/Support/Extension.def",
         "include/llvm/Support/VCSRevision.h",
     ],
     copts = llvm_copts,
     includes = ["include"],
     linkopts = select({
         "@bazel_tools//src/conditions:windows": [],
+        "@bazel_tools//src/conditions:freebsd": [
+            "-pthread",
+            "-lexecinfo",
+            "-ldl",
+            "-lm",
+        ],
         "//conditions:default": [
             "-pthread",
             "-ldl",
             "-lm",
         ],
     }),
     textual_hdrs = glob([
         "include/llvm/Support/*.def",