[Github][CI] Upload .ninja_log as an artifact

This enables using tools like https://github.com/nico/ninjatracing for
performance introspection.

Reviewers: 

Pull Request: llvm#135539

Author: boomanaiden154

.ci/monolithic-linux.sh

@@ -33,6 +33,7 @@ function at-exit {
 
   mkdir -p artifacts
   ccache --print-stats > artifacts/ccache_stats.txt
+  cp "${BUILD_DIR}"/.ninja_log artifacts/.ninja_log
 
   # If building fails there will be no results files.
   shopt -s nullglob

.ci/monolithic-windows.sh

@@ -32,6 +32,7 @@ function at-exit {
 
   mkdir -p artifacts
   sccache --show-stats >> artifacts/sccache_stats.txt
+  cp "${BUILD_DIR}"/.ninja_log artifacts/.ninja_log
 
   # If building fails there will be no results files.
   shopt -s nullglob