Disable install_test in macOS debug builds (RobotLocomotion#21876)

CI doesn't have enough disk space to handle this beast.

BUILD.bazel

@@ -4,13 +4,13 @@
 load("//tools/install:install.bzl", "install", "install_test")
 load("//tools/lint:lint.bzl", "add_lint_tests")
 load("//tools/skylark:py.bzl", "py_library")
+load("//tools/workspace:generate_file.bzl", "generate_file")
 
-package(
-    default_visibility = ["//visibility:public"],
-)
+package(default_visibility = ["//visibility:private"])
 
 exports_files([
     "CPPLINT.cfg",
+    "LICENSE.TXT",
     ".bazelproject",
     ".clang-format",
     ".drake-find_resource-sentinel",
@@ -23,6 +23,7 @@ exports_files([
 py_library(
     name = "module_py",
     srcs = ["__init__.py"],
+    visibility = ["//visibility:public"],
 )
 
 # Expose shared library for (a) installed binaries, (b) Drake Python bindings,
@@ -88,6 +89,7 @@ install(
     install_tests_script = _INSTALL_TEST_COMMANDS,
     data = ["package.xml"],
     docs = ["LICENSE.TXT"],
+    visibility = ["//visibility:public"],
     deps = [
         "//bindings/pydrake:install",
         "//common:install",
@@ -102,15 +104,34 @@ install(
     ],
 )
 
+generate_file(
+    name = "empty.txt",
+    content = "",
+)
+
 install_test(
     name = "install_test",
-    args = ["--install_tests_filename=$(location :{})".format(
-        _INSTALL_TEST_COMMANDS,
-    )],
-    data = [
-        ":install",
-        _INSTALL_TEST_COMMANDS,
-    ],
+    args = select({
+        "//tools/cc_toolchain:apple_debug": [
+            # The install_test on a CI macOS debug build uses too much disk
+            # space, so we'll skip it in that case.
+            "--install_tests_filename=$(location :empty.txt)",
+        ],
+        "//conditions:default": [
+            "--install_tests_filename=$(location :{})".format(
+                _INSTALL_TEST_COMMANDS,
+            ),
+        ],
+    }),
+    data = select({
+        "//tools/cc_toolchain:apple_debug": [
+            ":empty.txt",
+        ],
+        "//conditions:default": [
+            ":install",
+            _INSTALL_TEST_COMMANDS,
+        ],
+    }),
     tags = [
         # Running acceptance tests under coverage (kcov) probably burns more CI
         # time and flakiness compared to any upside.

tools/install/install_test.py

@@ -63,6 +63,13 @@ def main():
     with open(args.install_tests_filename, 'r') as f:
         lines = f.readlines()
 
+    # If all tests were disabled, exit early to avoid installing anything.
+    if not lines:
+        print()
+        print("WARNING: All install_test cases were disabled!")
+        print()
+        return 0
+
     # Add them as individual tests.
     test_case_names = []
     for one_line in lines: