Fix Windows find_package(libobs) and make CI hard-fail when the OBS module is missing

Root cause of the find_package(libobs) failure on Windows: OBS's own
modern-CMake Windows layout (obs-studio/cmake/windows/defaults.cmake sets
OBS_CMAKE_DESTINATION=cmake) installs libobs's CMake package config to
<prefix>/cmake/libobs/ -- a shape find_package(libobs CONFIG) never
searches under CMAKE_PREFIX_PATH. Verified empirically with
--debug-find-pkg=libobs: CMake's Config-mode search suffixes try
<prefix>/cmake/libobsConfig.cmake (no <name> subdirectory) and
<prefix>/libobs*/cmake/... (a <name>-prefixed dir first), never
<prefix>/cmake/<name>*/. This has nothing to do with the earlier "file
INSTALL cannot find obs-frontend-api.dll" error the bootstrap already
tolerates -- libobs is the first subdirectory obs-studio's modern
top-level CMakeLists.txt adds (well before UI), so libobs's own
install(EXPORT ...) rules already completed by the time that later,
unrelated install error aborts the script. macOS is unaffected
(OBS_CMAKE_DESTINATION=lib/cmake there, matching the standard
<prefix>/lib*/cmake/<name>*/ suffix), and so is Linux's libobs-dev
(/usr/lib/<arch>/cmake/libobs/, same standard suffix).

Fix: point libobs_DIR directly at the from-source Windows install when it
exists, bypassing find_package's path-search heuristics entirely. Also
fixed a secondary bug found while tracing this: the existing WIN32
locationless-OBS::libobs repair looked for obs.dll under
"<deps>/bin" instead of the actual OBS_EXECUTABLE_DESTINATION,
"<deps>/bin/64bit".

Also make the Windows and macOS "Show what was built" CI steps hard-fail
when the OBS adapter module is missing, instead of only printing a
message. Several recent "green" Windows runs silently shipped a
core-library-only build because of the bug above; nothing in CI caught
it, only a human reading the raw log by hand. Left Linux untouched (its
check is already a hard, non-"|| true" verification). Applied the same
hard-fail treatment to macOS: its bootstrap has been reliably building
the real module in CI (6/6 tests, per README), so there's no longer a
known legitimate reason for a silent core-only fallback there either --
the documented macOS packaging/bundle-loadability gap is a separate,
already-visible issue this check doesn't touch.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RL8abRmgFXkVASHkkqiJbE

CMakeLists.txt

@@ -136,6 +136,54 @@ find_package(LiveKit CONFIG REQUIRED)
 
 add_subdirectory(core)
 
+# On Windows, OBS's own modern-CMake install layout
+# (obs-studio/cmake/windows/defaults.cmake: OBS_CMAKE_DESTINATION=cmake)
+# installs libobs's CMake package config to <prefix>/cmake/<target>/ --
+# a shape find_package(<pkg> CONFIG) never searches under CMAKE_PREFIX_PATH.
+# CMake's documented Config-mode search suffixes include
+# "<prefix>/(cmake|CMake)/" (the file directly inside that dir, no <name>
+# subdirectory) and "<prefix>/<name>*/(cmake|CMake)/[...]" (a <name>-prefixed
+# directory first) -- neither matches "<prefix>/cmake/<name>*/". Verified
+# empirically: a find_package(libobs CONFIG) run with CMAKE_PREFIX_PATH
+# pointed at a directory laid out exactly like this (cmake/libobs/
+# libobsConfig.cmake underneath it) never even tries that path, confirmed
+# with --debug-find-pkg=libobs.
+#
+# macOS does not have this problem -- its OBS_CMAKE_DESTINATION is
+# "lib/cmake", so the package lands at <prefix>/lib/cmake/libobs/, which
+# matches the standard "<prefix>/lib*/cmake/<name>*/" suffix -- and neither
+# does Linux's libobs-dev, which installs to
+# /usr/lib/<arch-triplet>/cmake/libobs/, the same standard suffix. Windows is
+# the one platform whose own upstream install destination CMake's
+# find_package was never going to locate on its own; this is not caused by,
+# and is not fixed by, the earlier "file INSTALL cannot find
+# obs-frontend-api.dll" error tolerated in
+# cmake/common/buildspec_common.cmake's _setup_obs_studio -- libobs is the
+# FIRST subdirectory obs-studio's modern top-level CMakeLists.txt adds
+# (before libobs-d3d11/-winrt/-opengl, plugins, test/test-input and finally
+# UI), so libobs's own install(EXPORT ...) rules, including this Config file,
+# already ran to completion by the time cmake --install later aborts inside
+# UI/obs-frontend-api's install script.
+#
+# So: point find_package(libobs) directly at the from-source Windows install
+# rather than relying on path-search heuristics that were never going to find
+# it. Guarded by "NOT libobs_DIR" so an explicit -Dlibobs_DIR=... from a
+# developer with their own OBS SDK is never overridden, and by EXISTS so this
+# is a no-op whenever STPLUGIN_BOOTSTRAP_OBS=OFF or the bootstrap didn't
+# reach this point.
+if(OS_WINDOWS AND NOT libobs_DIR)
+    set(_stplugin_win_libobs_dir "${CMAKE_CURRENT_SOURCE_DIR}/.deps/cmake/libobs")
+    if(EXISTS "${_stplugin_win_libobs_dir}/libobsConfig.cmake")
+        set(libobs_DIR "${_stplugin_win_libobs_dir}" CACHE PATH
+            "Directory containing libobsConfig.cmake" FORCE)
+        message(STATUS
+            "libobs_DIR not set; OBS's Windows OBS_CMAKE_DESTINATION=cmake "
+            "does not match any of CMake's standard find_package Config-mode "
+            "search suffixes, so pointing it directly at the from-source "
+            "install: ${_stplugin_win_libobs_dir}")
+    endif()
+endif()
+
 find_package(libobs QUIET)
 
 # The imported OBS::libobs target can come back without a location. OBS 30.0.2
@@ -176,8 +224,15 @@ if(libobs_FOUND AND TARGET OBS::libobs)
                 message(STATUS "OBS::libobs had no imported location; pointed it at ${_stplugin_obs_binary}")
             endif()
         elseif(WIN32)
+            # obs-studio/cmake/windows/defaults.cmake sets
+            # OBS_EXECUTABLE_DESTINATION=bin/64bit (the RUNTIME destination
+            # obs.dll installs to as a SHARED_LIBRARY target) and
+            # OBS_LIBRARY_DESTINATION=lib (the ARCHIVE destination for
+            # obs.lib) -- not a flat "bin", which is what upstream
+            # obs-plugintemplate's own equivalent macOS-only repair never had
+            # to get right.
             find_file(_stplugin_obs_implib_found obs.lib PATHS "${_stplugin_deps}/lib" NO_DEFAULT_PATH)
-            find_file(_stplugin_obs_dll_found obs.dll PATHS "${_stplugin_deps}/bin" NO_DEFAULT_PATH)
+            find_file(_stplugin_obs_dll_found obs.dll PATHS "${_stplugin_deps}/bin/64bit" NO_DEFAULT_PATH)
             if(_stplugin_obs_implib_found)
                 set_target_properties(OBS::libobs PROPERTIES IMPORTED_IMPLIB "${_stplugin_obs_implib_found}")
                 if(_stplugin_obs_dll_found)