Revert "Default to use llvm16"

This reverts commit 2cc2b392c9ef02f363850de20e3938676e8be48f.

Reason for revert: Blocks roll into Chromium

Change-Id: Icd2bd2ff6d737b083e2e4e7b0d80bb023420aab2
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/73108
Reviewed-by: Yuxin Hu <yuxinhu@google.com>
Commit-Queue: Shahbaz Youssefi <syoussefi@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Shahbaz Youssefi <syoussefi@google.com>
diff --git a/src/Reactor/BUILD.gn b/src/Reactor/BUILD.gn
index dcb1361..67dfeb0 100644
--- a/src/Reactor/BUILD.gn
+++ b/src/Reactor/BUILD.gn
@@ -307,7 +307,7 @@
 
 if (supports_llvm) {
   swiftshader_source_set("swiftshader_llvm_reactor") {
-    llvm_dir = "../../third_party/llvm-16.0"
+    llvm_dir = "../../third_party/llvm-10.0"
 
     deps = [
       ":swiftshader_reactor_base",