[antlir/metalos][oss] fix some third party deps builds

Summary: Title

Test Plan:
```name="Third-party deps of bootloader build"
❯ buck build --keep-going //metalos/bootloader:metalos-bootloader
Action failed: metalos//metalos/lib/tracing:metalos_tracing (rustc rlib)
Local command returned non-zero exit code 1
Reproduce locally: `env -- 'BUCK_SCRATCH_PATH=buck-out/v2/tmp/metalos/e85947776b662505/rustc/rlib' /usr/bin/env 'PYTHONP ...<omitted>... 03749/metalos/lib/tracing/__metalos_tracing__/rlib-static-static-link/metalos_tracing-link-diag.args (run `buck2 log what-failed` to get the full command)`
stdout:
stderr:
error: external crate `fbinit` unused in `metalos_tracing`: remove the dependency or add `use fbinit as _;`
  |
  = note: requested on the command line with `-F unused-crate-dependencies`

error: aborting due to 1 previous error

Action failed: metalos//metalos/lib/tracing:metalos_tracing (rustc metadata [static])
Local command returned non-zero exit code 1
Reproduce locally: `env -- 'BUCK_SCRATCH_PATH=buck-out/v2/tmp/metalos/e85947776b662505/rustc/_buck_749b01f6d1bd8e8c' /us ...<omitted>... tracing/__metalos_tracing__/rlib-static-static-metadata-full/metalos_tracing-metadata-full-diag.args (run `buck2 log what-failed` to get the full command)`
stdout:
stderr:
error: external crate `fbinit` unused in `metalos_tracing`: remove the dependency or add `use fbinit as _;`
  |
  = note: requested on the command line with `-F unused-crate-dependencies`

error: aborting due to 1 previous error

Build ID: 4bdfc708-d862-427e-b07e-87e3205a72cf
Network: Up: 0B  Down: 0B
Jobs completed: 5290. Time elapsed: 29.0s.
Cache hits: 0%. Commands: 1282 (cached: 0, remote: 0, local: 1282)
BUILD FAILED
Failed to build 'metalos//metalos/lib/tracing:metalos_tracing (prelude//platforms:default#904931f735703749)'
```

Differential Revision: D59928725

antlir/bzl/build_defs_impl.bzl

@@ -17,19 +17,26 @@ def _third_party_library(project, rule = None, platform = None):
     if not rule:
         rule = project
 
+    # TODO: third party deps should be consumable from the cell which is calling
+    # this function so that deps aren't pinned to whatever ships in antlir, but
+    # while metalos has deps on some antlir rust targets, we can't do this (or
+    # we get mismatched type errors with duplicate crates)
+    cell = "antlir"
+
     if platform == "python" or platform == "pypi":
         if not rule == project:
             fail("python dependencies must omit rule or be identical to project")
-        return "antlir//third-party/python:" + project
+
+        return cell + "//third-party/python:" + project
 
     if platform == "rust":
         if not rule == project:
             fail("rust dependencies must omit rule or be identical to project")
 
-        return "antlir//third-party/rust:" + project
+        return cell + "//third-party/rust:" + project
 
     if platform == "antlir":
-        return "//third-party/antlir/{project}:{rule}".format(
+        return cell + "//third-party/antlir/{project}:{rule}".format(
             project = project,
             rule = rule,
         )