Respect ENABLE_CLANG_TIDY instead of always pulling the monorepo's modules.

stinkytofu declares option(ENABLE_CLANG_TIDY ... OFF) and then unconditionally
does

    list(APPEND CMAKE_MODULE_PATH ".../../../cmake/modules")
    include(ClangTidy)
    add_clang_tidy_custom_target()

That path only resolves inside the rocm-libraries monorepo checkout. When
stinkytofu is built from its own release tarball -- which is how it is consumed
here, co-unpacked alongside hipblaslt -- the shared cmake/modules directory is
not present and configuration dies with

    CMake Error at CMakeLists.txt:366 (include): could not find load file: ClangTidy
    CMake Error at CMakeLists.txt:367 (add_clang_tidy_custom_target)

Guarding the block with the option it already defines fixes the standalone
case and is a no-op for the monorepo build, where the option can still be
turned on.
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -362,9 +362,11 @@
 # clang-tidy
 # --------------------------------------------------------------------------- #
 option(ENABLE_CLANG_TIDY "Enable clang-tidy targets" OFF)
-list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../../cmake/modules")
-include(ClangTidy)
-add_clang_tidy_custom_target()
+if(ENABLE_CLANG_TIDY)
+    list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../../cmake/modules")
+    include(ClangTidy)
+    add_clang_tidy_custom_target()
+endif()
 
 # Build-tree export so find_package() works without installing.
 # Write targets to stinkytofu-targets.cmake (not stinkytofuConfig.cmake) to