Use correct Java version for Maven build tools

Author: olafurpg

.github/workflows/ci.yml

@@ -8,6 +8,7 @@ jobs:
   test:
     runs-on: ${{ matrix.os }}
     strategy:
+      fail-fast: false
       matrix:
         # NOTE(olafurpg) Windows is not enabled because it times out due to reasons I don't understand.
         # os: [windows-latest, ubuntu-latest]

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

@@ -5,7 +5,6 @@ import java.nio.file.Path
 import java.nio.file.Paths
 
 import scala.collection.mutable.ListBuffer
-import scala.util.Properties
 
 import com.sourcegraph.scip_java.Embedded
 import com.sourcegraph.scip_java.commands.IndexCommand
@@ -36,14 +35,15 @@ class MavenBuildTool(index: IndexCommand) extends BuildTool("Maven", index) {
         else {
           "mvn"
         }
+      val start = System.nanoTime()
       val buildCommand = ListBuffer.empty[String]
       val executable = Embedded.customJavac(
         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.
-        Properties.isJavaAtLeast(11)
+        GradleJavaToolchains.isJavaAtLeast(SystemJavaVersion.detect(), "11")
       )
       buildCommand ++=
         List(

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

@@ -0,0 +1,26 @@
+package com.sourcegraph.scip_java.buildtools
+
+import java.nio.file.Files
+
+import com.sourcegraph.scip_java.Embedded
+
+object SystemJavaVersion {
+  def detect(): String = {
+    val tmp = Files.createTempDirectory("java-version")
+    val jar = Embedded.semanticdbJar(tmp)
+    try {
+      os.proc(
+          "java",
+          "-cp",
+          jar.toString(),
+          "com.sourcegraph.semanticdb_javac.PrintJavaVersion"
+        )
+        .call()
+        .out
+        .text()
+        .trim()
+    } finally {
+      Files.deleteIfExists(jar)
+    }
+  }
+}

semanticdb-javac/src/main/java/com/sourcegraph/semanticdb_javac/PrintJavaVersion.java

@@ -0,0 +1,7 @@
+package com.sourcegraph.semanticdb_javac;
+
+public class PrintJavaVersion {
+  public static void main(String[] args) {
+    System.out.print(System.getProperty("java.version"));
+  }
+}