Revert^2 "Upgrade to clang-r547379"

This reverts commit edd39aee55e758219a1c91f4db4399d796ddb5f8.

Reason for revert: reland compiler update

Change-Id: I51bd7bd16df5a41afb847587f952c9756070627c
diff --git a/cc/config/global.go b/cc/config/global.go
index a309dc0..19ed8e7 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -383,8 +383,8 @@
 
 	// prebuilts/clang default settings.
 	ClangDefaultBase         = "prebuilts/clang/host"
-	ClangDefaultVersion      = "clang-r536225"
-	ClangDefaultShortVersion = "19"
+	ClangDefaultVersion      = "clang-r547379"
+	ClangDefaultShortVersion = "20"
 
 	// Directories with warnings from Android.bp files.
 	WarningAllowedProjects = []string{