Explicitly list the java files for what we need to generate header.

lib/build.gradle

@@ -285,5 +285,35 @@ task checkCurrentJavaVersion() {
 
 task generateHeaderFilesFromJavaWrapper(type: Exec) {
     workingDir "${projectDir}/src/main/java/org/kiwix/"
-    commandLine 'bash', '-c', "javac -h ${buildDir}/include/javah_generated/ -d ${buildDir}/libzim/ libzim/*.java libkiwix/*.java"
+    commandLine 'bash', '-c', "javac -h ${buildDir}/include/javah_generated/ -d ${buildDir}/libzim/ ${getLibzimFiles()} ${getLibkiwixFiles()}"
+}
+
+String getLibkiwixFiles() {
+    return "${projectDir}/src/main/java/org/kiwix/libkiwix/Book.java " +
+        "${projectDir}/src/main/java/org/kiwix/libkiwix/Bookmark.java " +
+        "${projectDir}/src/main/java/org/kiwix/libkiwix/Filter.java " +
+        "${projectDir}/src/main/java/org/kiwix/libkiwix/JNIICU.java " +
+        "${projectDir}/src/main/java/org/kiwix/libkiwix/Illustration.java " +
+        "${projectDir}/src/main/java/org/kiwix/libkiwix/JNIKiwixException.java " +
+        "${projectDir}/src/main/java/org/kiwix/libkiwix/Library.java " +
+        "${projectDir}/src/main/java/org/kiwix/libkiwix/Manager.java " +
+        "${projectDir}/src/main/java/org/kiwix/libkiwix/Server.java"
+}
+
+String getLibzimFiles() {
+    return "${projectDir}/src/main/java/org/kiwix/libzim/Archive.java " +
+        "${projectDir}/src/main/java/org/kiwix/libzim/Blob.java " +
+        "${projectDir}/src/main/java/org/kiwix/libzim/DirectAccessInfo.java " +
+        "${projectDir}/src/main/java/org/kiwix/libzim/EntryIterator.java " +
+        "${projectDir}/src/main/java/org/kiwix/libzim/Entry.java " +
+        "${projectDir}/src/main/java/org/kiwix/libzim/Item.java " +
+        "${projectDir}/src/main/java/org/kiwix/libzim/Query.java " +
+        "${projectDir}/src/main/java/org/kiwix/libzim/Searcher.java " +
+        "${projectDir}/src/main/java/org/kiwix/libzim/SearchIterator.java" +
+        "${projectDir}/src/main/java/org/kiwix/libzim/Search.java" +
+        "${projectDir}/src/main/java/org/kiwix/libzim/SuggestionItem.java" +
+        "${projectDir}/src/main/java/org/kiwix/libzim/SuggestionIterator.java" +
+        "${projectDir}/src/main/java/org/kiwix/libzim/SuggestionSearcher.java" +
+        "${projectDir}/src/main/java/org/kiwix/libzim/SuggestionSearch.java" +
+        "${projectDir}/src/main/java/org/kiwix/libzim/ZimFileFormatException.java"
 }