Add filegroup support to notice property.

Also, replace all notice file references with the parent directory
pattern(../) with filegroups.

Bug: 118899640
Test: Manual build
Change-Id: I841345d747f41a3bb5beea66ad87a979734c39a4
diff --git a/Android.bp b/Android.bp
index ef42c84..151e98b 100644
--- a/Android.bp
+++ b/Android.bp
@@ -435,7 +435,7 @@
             src: "prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8/x86_64-w64-mingw32/lib/libwinpthread.a",
         },
     },
-    notice: "../../prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8/licenses/mingw-w64-svn-r5861/mingw-w64-libraries/winpthreads/COPYING",
+    notice: ":mingw-libwinpthread-notice",
 }
 
 toolchain_library {