[bazel] -lrt is not available on Android.

[rupprecht]

Note: this uses @platforms//os:android and not @bazel_tools//src/conditions:android because android is not one of the configs listed in @bazel_tools//src/conditions.

We should really be using @platforms in place of @bazel_tools//src/conditions everywhere, but that's a larger change, especially in llvm/config.bzl which has OS+CPU mappings that don't exist in @platforms. I have a pending change to do that as a followup.

[GMNGeoffrey]

LGTM

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

hdrs = glob([
         "include/llvm/ExecutionEngine/Orc/RPC/*.h",
     ]) + [
         "include/llvm-c/LLJIT.h",
         "include/llvm-c/Orc.h",
         "include/llvm-c/OrcEE.h",
     ],
     copts = llvm_copts,
     linkopts = select({
+        "@platforms//os:android": [],
         "@bazel_tools//src/conditions:windows": [],
         "@bazel_tools//src/conditions:freebsd": [],
         "@bazel_tools//src/conditions:darwin": [],
         "//conditions:default": [
             "-lrt",
         ],
     }),
     deps = [
srcs = glob([
         "lib/ExecutionEngine/Orc/TargetProcess/*.cpp",
         "lib/ExecutionEngine/Orc/TargetProcess/*.h",
     ]),
     hdrs = glob([
         "include/llvm/ExecutionEngine/Orc/TargetProcess/*.h",
     ]),
     copts = llvm_copts,
     linkopts = select({
+        "@platforms//os:android": [],
         "@bazel_tools//src/conditions:windows": [],
         "@bazel_tools//src/conditions:freebsd": [],
         "@bazel_tools//src/conditions:darwin": [],
         "//conditions:default": [
             "-lrt",
         ],
     }),
     deps = [