SOLR-17490: Check for existence of perl executable and skip if it doe…

…snt exist (#2753)

gradle/documentation/changes-to-html.gradle

@@ -76,6 +76,13 @@ class ChangesToHtmlTask extends DefaultTask {
 
   def toHtml(File versionsFile) {
     def output = new ByteArrayOutputStream()
+
+    // Check if the perl executable exists
+    if (!perlExists()) {
+        logger.warn("WARNING: Perl is not installed, skipping creating Changes.html")
+        return
+    }
+
     def result = project.exec {
       executable project.externalTool("perl")
       standardInput changesFile.newInputStream()
@@ -114,4 +121,14 @@ class ChangesToHtmlTask extends DefaultTask {
       throw new GradleException("Changes file ${changesFile} or Doap file ${changesDoapFile} not found.")
     }
   }
+
+  def perlExists() {
+    try {
+        def process = "perl -v".execute()
+        process.waitFor()
+        return process.exitValue() == 0
+    } catch (Exception e) {
+        return false
+    }
+  }
 }