thread context scratch system; converge on transition idiom in sample code

build_with_clang.bat

@@ -1,11 +1,11 @@
 @echo off
 
 echo ~~~ Metadesk Build ~~~
+set src=%cd%
+
 rem TODO(mal): Review these warnings
 set accepted_clang_warnings=-Wno-deprecated-declarations -Wno-pointer-sign -Wno-writable-strings -Wno-unknown-warning-option
-set compile_flags=-I../source/ %accepted_clang_warnings%
-
-set src=%cd%
+set compile_flags=-I%src%/source/ %accepted_clang_warnings%
 
 if not exist build mkdir build
 pushd build