[workspace] No need to install spdlog CMake files (RobotLocomotion#17287

)

* [workspace] No need to install spdlog CMake files

We only build from source in wheel builds, which don't care about this.

tools/workspace/spdlog/BUILD.bazel

@@ -2,12 +2,4 @@
 
 load("//tools/lint:lint.bzl", "add_lint_tests")
 
-exports_files(
-    [
-        "spdlog-config.cmake",
-        "spdlog-config-version.cmake",
-    ],
-    visibility = ["@spdlog//:__pkg__"],
-)
-
 add_lint_tests()

tools/workspace/spdlog/package.BUILD.bazel

@@ -6,7 +6,6 @@
 load(
     "@drake//tools/install:install.bzl",
     "install",
-    "install_files",
 )
 
 licenses(["notice"])  # MIT
@@ -92,27 +91,12 @@ cc_library(
     visibility = ["//visibility:public"],
 )
 
-CMAKE_PACKAGE = "spdlog"
-
-install_files(
-    name = "install_cmake_config",
-    dest = "lib/cmake/{}".format(CMAKE_PACKAGE),
-    files = [
-        "@drake//tools/workspace/spdlog:{}-config.cmake".format(CMAKE_PACKAGE),  # noqa
-        "@drake//tools/workspace/spdlog:{}-config-version.cmake".format(CMAKE_PACKAGE),  # noqa
-    ],
-    strip_prefix = ["**/"],
-    allowed_externals = ["@drake//:.bazelproject"],
-    visibility = ["//visibility:private"],
-)
-
 install(
     name = "install",
     targets = [":libdrake_spdlog.so"],
-    hdr_dest = "include/" + CMAKE_PACKAGE,
+    hdr_dest = "include/spdlog",
     hdr_strip_prefix = ["include"],
     hdrs = _HDRS,
     docs = ["LICENSE"],
-    deps = [":install_cmake_config"],
     visibility = ["//visibility:public"],
 )

tools/workspace/spdlog/repository.bzl

@@ -28,7 +28,7 @@ def _impl(repo_ctx):
 
 spdlog_repository = repository_rule(
     attrs = {
-        # The next two attributes are used only when we take the branch for
+        # The next several attributes are used only when we take the branch for
         # setup_pkg_config_repository in the above logic.
         "modname": attr.string(
             default = "spdlog",
@@ -55,10 +55,6 @@ install(name = "install")
             # Here, we elect to use the same version as Ubuntu 20.04, even
             # though it is not the newest revision.  Sticking with a single,
             # older revision helps reduce spurious CI failures.
-            #
-            # In the unlikely event that you update the version here, fix up
-            # the two spdlog-*.cmake files in this directory, and revisit all
-            # of the version compatibility matrix in spdlog/repository.bzl.
             default = "v1.5.0",
         ),
         "commit_pin": attr.int(