Package clang-scan-deps

Bug: android/ndk#1853

clang-scan-deps is 88M because the backends for all targets are included in clang-scan-deps.  Linking of backends was added by https://reviews.llvm.org/D103519 - to support PCH.

Change-Id: I9266488056401528ddf96a7434c02177c0242a72
Test: presubmit

do_build.py

@@ -399,6 +399,7 @@ def package_toolchain(toolchain_builder: LLVMBuilder,
         'clang-check' + ext,
         'clang-cl' + ext,
         'clang-format' + ext,
+        'clang-scan-deps' + ext,
         'clang-tidy' + ext,
         'clangd' + ext,
         'dsymutil' + ext,