Fix clang header dependency for versioner

Versioner is now a prebuilt in prebuilts/clang-tools and that project
has the Clang headers packaged with it.  Use that dependency instead of
external/clang/lib/Headers.  Use the linux-x86 path for both Linux and
Darwin since they are both the same.

Test: presubmit
Change-Id: I01ad4c05fe3301a2fdad3662377f78694af6cd81
diff --git a/libc/versioner-dependencies/common/clang-builtins b/libc/versioner-dependencies/common/clang-builtins
index 7bd481c..148dd2b 120000
--- a/libc/versioner-dependencies/common/clang-builtins
+++ b/libc/versioner-dependencies/common/clang-builtins
@@ -1 +1 @@
-../../../../external/clang/lib/Headers/
\ No newline at end of file
+../../../../prebuilts/clang-tools/linux-x86/clang-headers
\ No newline at end of file