Make it an error to have a cc_shared_library with no deps

A cc_shared_library with no deps doesn't provide anything on the build graph, it would be an empty shared library file.

RELNOTES:none
PiperOrigin-RevId: 508597495
Change-Id: Ied80243500b804071b88a6df5c0fc9c8bbdd0f28

src/main/starlark/builtins_bzl/common/cc/experimental_cc_shared_library.bzl

@@ -418,6 +418,12 @@ def _get_deps(ctx):
     if not len(deps):
         deps = ctx.attr.roots
 
+    if len(deps) == 0:
+        fail(
+            "'cc_shared_library' must have at least one dependency in 'deps' (or 'roots')",
+            attr = "deps",
+        )
+
     return deps
 
 def _cc_shared_library_impl(ctx):

src/main/starlark/tests/builtins_bzl/cc/cc_shared_library/test_cc_shared_library/BUILD.builtin_test

@@ -492,3 +492,9 @@ no_exporting_static_lib_test(
     name = "no_exporting_static_lib_test",
     target_under_test = ":lib_with_no_exporting_roots",
 )
+
+build_failure_test(
+    name = "shared_library_without_deps",
+    message = "'cc_shared_library' must have at least one dependency in 'deps' (or 'roots')",
+    target_under_test = "//src/main/starlark/tests/builtins_bzl/cc/cc_shared_library/test_cc_shared_library/failing_targets:failing_with_no_deps_so",
+)

src/main/starlark/tests/builtins_bzl/cc/cc_shared_library/test_cc_shared_library/failing_targets/BUILD.builtin_test

@@ -100,3 +100,8 @@ cc_shared_library(
     ],
     tags = TAGS,
 )
+
+cc_shared_library(
+    name = "failing_with_no_deps_so",
+    tags = TAGS,
+)