Revert "Upgrade to clang-r547379"

This reverts commit 59d89c4b2a3bafdd08ba0095e231493d60ecb04e.

Reason for revert: Droidmonitor created revert due to b/394414383. Will be verifying through ABTD before submission.

Change-Id: I2b6d392cdfd85f906b673f8bb568a15d110dfb92
diff --git a/cc/config/global.go b/cc/config/global.go
index 19ed8e7..a309dc0 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-r547379"
-	ClangDefaultShortVersion = "20"
+	ClangDefaultVersion      = "clang-r536225"
+	ClangDefaultShortVersion = "19"
 
 	// Directories with warnings from Android.bp files.
 	WarningAllowedProjects = []string{
diff --git a/cc/config/x86_linux_host.go b/cc/config/x86_linux_host.go
index c070050..287967c 100644
--- a/cc/config/x86_linux_host.go
+++ b/cc/config/x86_linux_host.go
@@ -41,6 +41,7 @@
 	}
 
 	linuxMuslCflags = []string{
+		"-D_LIBCPP_HAS_MUSL_LIBC",
 		"-DANDROID_HOST_MUSL",
 		"-nostdlibinc",
 		"--sysroot /dev/null",