Export LLVM_RELEASE_VERSION

Test: m -j libc; check out/soong/make_vars-*.mk
Change-Id: Ic29407d8b2ecc69f8d95102bca81bec3f0c5012b

cc/makevars.go

@@ -29,6 +29,7 @@ func init() {
 }
 
 func makeVarsProvider(ctx android.MakeVarsContext) {
+	ctx.Strict("LLVM_RELEASE_VERSION", "${config.ClangShortVersion}")
 	ctx.Strict("LLVM_PREBUILTS_VERSION", "${config.ClangVersion}")
 	ctx.Strict("LLVM_PREBUILTS_BASE", "${config.ClangBase}")
 	ctx.Strict("LLVM_PREBUILTS_PATH", "${config.ClangBin}")