Use prebuilt bionic versioner

This commit replaces versioner host binary (built just-in-time) with
a prebuilt binary under `prebuilts/clang-tools/${OS}/bin/versioner`.
This is a part of the effort to switch to clang-r339409b.

See also.
https://android-review.googlesource.com/c/platform/bionic/+/799321

Bug: 113263746
Test: make checkbuild
Change-Id: Ia845e1c01d8b8084d00bdc4af706e867e1599863
diff --git a/cc/ndk_headers.go b/cc/ndk_headers.go
index a7d6e04..8177ff1 100644
--- a/cc/ndk_headers.go
+++ b/cc/ndk_headers.go
@@ -44,7 +44,7 @@
 )
 
 func init() {
-	pctx.HostBinToolVariable("versionerCmd", "versioner")
+	pctx.SourcePathVariable("versionerCmd", "prebuilts/clang-tools/${config.HostPrebuiltTag}/bin/versioner")
 }
 
 // Returns the NDK base include path for use with sdk_version current. Usable with -I.