Silence renderscript build log spam.

No-one's going to clean up unused-but-set variable warnings in a
decade-old copy of LLVM...

Removes stuff like:
```
In file included from frameworks/compile/mclinker/lib/Target/AArch64/AArch64GOT.cpp:9:
In file included from frameworks/compile/mclinker/lib/Target/AArch64/AArch64GOT.h:15:
external/llvm/include/llvm/ADT/DenseMap.h:105:14: warning: variable 'NumEntries' set but not used [-Wunused-but-set-variable]
    unsigned NumEntries = getNumEntries();
             ^
```

Test: treehugger
Change-Id: I4f7b1147bc3719a2147f7a068f31444e8e95e5be

1 files changed, 1 insertions, 3 deletions

diff --git a/Android.bp b/Android.bp
index 5efa226..7eb6183 100644
--- a/Android.bp
+++ b/Android.bp
@@ -35,9 +35,7 @@ cc_defaults {
 
     cppflags: [
         "-Wall",
-        "-Wno-unused-parameter",
-        "-Wno-unused-private-field",
-        "-Wno-unused-const-variable",
+        "-Wno-unused",
         "-Werror",
 
         //To enable asserts: