Revert "[ci] run-tests: build:$PATH -> $PATH:build"

This reverts commit e9ff0ae1.

ci/run-tests.bash

@@ -19,7 +19,7 @@ then
 fi
 
 # Add built batsched in PATH
-export PATH="${PATH}:$(realpath ./build)"
+export PATH=$(realpath ./build):${PATH}
 
 # Set TEST_ROOT so simulation input files can be found
 export TEST_ROOT=$(realpath ./test)