Use reproducible time stamps for Maven build artifacts

Unfortunately, JAR files store time stamps of the files inside them.
These time stamps depend on the build time of these files hence breaking
bit for bit reproducibility. By setting all time stamps to a predefined
value and removing superfluous build artifacts this issue can be
avoided. Conventionally, UNIX time stamp 1 signifies an intentionally
set time stamp (in contrast to UNIX time stamp 0) which has no meaning
and is easy to recognize.

Author: ibbem

default.nix

@@ -67,6 +67,7 @@ pkgs.stdenv.mkDerivation rec {
       then ''
         mvn javadoc:javadoc
         JEKYLL_ENV=production PAGES_REPO_NWO=VariantSync/DiffDetective JEKYLL_BUILD_REVISION= github-pages build
+        rm -rf _site/target
       ''
       else ""
     }

pom.xml

@@ -13,6 +13,8 @@
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
         <maven.compiler.source>17</maven.compiler.source>
         <maven.compiler.target>17</maven.compiler.target>
+        <!-- Override the time stamps of build artifacts to ensure reproducibility -->
+        <project.build.outputTimestamp>1</project.build.outputTimestamp>
     </properties>
 
     <build>