Change the dates of source files before each build, to avoid useless rebuild

.gitlab-ci.yml

@@ -10,6 +10,11 @@ before_script:
   - whoami
   - mkdir -p build/
   - cd build/
+  # When we extract the artifacts from a previous build, the timestamp of all target are identicall to
+  # the timestamps of the generated source files (like biboumi.h, etc), so Makefile thinks the targets
+  # are not up to date, and everything is rebuilt.  We change the modification time of all these files
+  # to be 15 minutes older, to avoid any unnecessary building.
+  - find . \( -name \*.hpp -or -name \*.h -or -name \*.cpp \) -exec touch -r {} -d '-15 minute' {} \;
 
 variables:
   COMPILER: "g++"