Clean up Java 17 fixes

Author: olafurpg

scip-java/src/main/scala/com/sourcegraph/scip_java/buildtools/GradleBuildTool.scala

@@ -126,9 +126,8 @@ class GradleBuildTool(index: IndexCommand) extends BuildTool("Gradle", index) {
   }
 
   private def initScript(toolchains: GradleJavaToolchains, tmp: Path): Path = {
-    val executableJavacPath = toolchains.executableJavacPath()
     val executable =
-      executableJavacPath match {
+      toolchains.executableJavacPath() match {
         case Some(path) =>
           s"options.forkOptions.executable = '$path'"
         case None =>
@@ -161,7 +160,6 @@ class GradleBuildTool(index: IndexCommand) extends BuildTool("Gradle", index) {
           |      tasks.withType(JavaCompile) {
           |        options.fork = true
           |        options.incremental = false
-          |        System.out.println("JAVA VERSION " + System.getProperty("java.version"))
           |        $executable
           |      }
           |    }

scip-java/src/main/scala/com/sourcegraph/scip_java/buildtools/MavenBuildTool.scala

@@ -41,8 +41,6 @@ class MavenBuildTool(index: IndexCommand) extends BuildTool("Maven", index) {
         index.workingDirectory,
         index.finalTargetroot(defaultTargetroot),
         tmp,
-        // TODO: infer Java version from `java -version` because it may not
-        // match the Java version that's used by the current process.
         GradleJavaToolchains.isJavaAtLeast(SystemJavaVersion.detect(), "11")
       )
       buildCommand ++=

scip-java/src/main/scala/com/sourcegraph/scip_java/buildtools/SystemJavaVersion.scala

@@ -5,6 +5,10 @@ import java.nio.file.Files
 import com.sourcegraph.scip_java.Embedded
 
 object SystemJavaVersion {
+  // Returns the output of `System.getProperty("java.version")` from a fresh JVM
+  // instance using the system JVM installation. We can't use this process since
+  // it may be running on a separate JVM process (that's the case when we run
+  // `sbt test` in this build at least).
   def detect(): String = {
     val tmp = Files.createTempDirectory("java-version")
     val jar = Embedded.semanticdbJar(tmp)