Update stage 1 compiler to r450784b

Test: presubmit
Bug: 219872355
Change-Id: I1ae718f432eb0999e7f0a288b0bd5ea0e650a66f
diff --git a/constants.py b/constants.py
index d5efef5..7f21969 100644
--- a/constants.py
+++ b/constants.py
@@ -21,7 +21,7 @@
 MAC_MIN_VERSION: str = '10.14'
 
 # This is the baseline stable version of Clang to start our stage-1 build.
-CLANG_PREBUILT_VERSION: str = 'clang-r450784'
+CLANG_PREBUILT_VERSION: str = 'clang-r450784b'
 
 # This is the ndk version used to build runtimes.
 NDK_VERSION: str = 'r23'