manifest: track our own  external/minigbm

Change-Id: I84cc75a20633d0c34e69e6a3f8e5097b314db5b4
diff --git a/omni-aosp.xml b/omni-aosp.xml
index 9de8fd7..438864d 100644
--- a/omni-aosp.xml
+++ b/omni-aosp.xml
@@ -27,6 +27,7 @@
 
     <project path="external/drm_hwcomposer" name="android_external_drm_hwcomposer" remote="omnirom" revision="android-12.1" />
     <project path="external/libdrm" name="android_external_libdrm" remote="omnirom" revision="android-12.1" />
+    <project path="external/minigbm" name="android_external_minigbm" remote="omnirom" revision="android-12.1" />
 
     <project path="frameworks/av" name="android_frameworks_av" remote="omnirom" revision="android-12.1" />
     <project path="frameworks/base" name="android_frameworks_base" remote="omnirom" revision="android-12.1" />