ci: strip the non-relocatable OBS build tree before caching .deps

The obs-studio sub-build's out-of-source CMakeCache.txt
(.deps/obs-studio-*/build_*) bakes in the job's absolute checkout
path. Caching it as-is (from the previous .deps caching commit)
meant every run's first configure attempt hard-failed with:

  CMake Error: The current CMakeCache.txt directory ... is different
  than the directory ... where CMakeCache.txt was created.

Confirmed live in run 3091 (commit 1f342b1): this was silently
self-healing, since windows-build.ps1's existing fallback
(-DSTPLUGIN_BOOTSTRAP_OBS=OFF) still found the already-installed,
path-independent libobs package and the build succeeded anyway -- but
every run paid for one guaranteed-failed configure and printed a
misleading "::warning::OBS SDK bootstrap failed" that isn't actually
true. Delete only the build tree, after libobs is already built and
installed from it, so nothing path-dependent survives into the cache.

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

.gitea/workflows/build.yml

@@ -85,6 +85,25 @@ jobs:
       - name: Configure, build, test, verify
         run: .gitea/scripts/macos-build.sh
 
+      - name: Drop non-relocatable OBS build tree before caching
+        # cmake/common/buildspec_common.cmake's obs-studio sub-build writes
+        # an out-of-source CMakeCache.txt (.deps/obs-studio-*/build_*) that
+        # bakes in this job's absolute checkout path. The next run's
+        # checkout lands at a *different* absolute path, so restoring that
+        # directory from the cache above makes CMake refuse to reconfigure
+        # it ("CMakeCache.txt directory ... is different than the directory
+        # ... where CMakeCache.txt was created"). Everything that actually
+        # needs to survive between runs -- the extracted source, and the
+        # already-installed libobs package under .deps/cmake, .deps/include,
+        # .deps/lib -- has no such path baked in and is unaffected. Delete
+        # only the intermediate build tree, after it has already done its
+        # job (libobs is built and installed by this point), so the cache
+        # saved at the end of this job contains nothing that requires the
+        # path it was created under.
+        if: always()
+        continue-on-error: true
+        run: rm -rf .deps/obs-studio-*/build_*
+
       - name: Upload plugin
         continue-on-error: true
         uses: actions/upload-artifact@v3
@@ -123,6 +142,22 @@ jobs:
         shell: powershell
         run: ./.gitea/scripts/windows-build.ps1
 
+      - name: Drop non-relocatable OBS build tree before caching
+        # See the matching step in the macOS job above. Confirmed live on
+        # this runner: caching .deps/obs-studio-30.0.2/build_x86 as-is made
+        # every run's first configure attempt fail with a path mismatch
+        # against the job that populated the cache, falling back to
+        # -DSTPLUGIN_BOOTSTRAP_OBS=OFF and only succeeding because the
+        # already-installed libobs package (path-independent) was still
+        # found. That fallback masked the problem behind a misleading
+        # "::warning::OBS SDK bootstrap failed" every run instead of fixing
+        # it. Deleting the build tree here, after libobs is already built
+        # and installed, is the actual fix.
+        if: always()
+        continue-on-error: true
+        shell: powershell
+        run: Remove-Item -Recurse -Force .deps\obs-studio-*\build_* -ErrorAction SilentlyContinue
+
       - name: Upload plugin
         continue-on-error: true
         uses: actions/upload-artifact@v3