Terminate --javacopts in tests with --

PiperOrigin-RevId: 179841278
diff --git a/src/java_tools/buildjar/javatests/com/google/devtools/build/buildjar/VanillaJavaBuilderTest.java b/src/java_tools/buildjar/javatests/com/google/devtools/build/buildjar/VanillaJavaBuilderTest.java
index 784d0ba..b64e2d8 100644
--- a/src/java_tools/buildjar/javatests/com/google/devtools/build/buildjar/VanillaJavaBuilderTest.java
+++ b/src/java_tools/buildjar/javatests/com/google/devtools/build/buildjar/VanillaJavaBuilderTest.java
@@ -83,6 +83,7 @@
             ImmutableList.of(
                 "--javacopts",
                 "-Xep:FallThrough:ERROR",
+                "--",
                 "--sources",
                 source.toString(),
                 "--source_jars",
@@ -127,6 +128,7 @@
                 "--javacopts",
                 "-Xlint:all",
                 "-Werror",
+                "--",
                 "--sources",
                 source.toString(),
                 "--output",
@@ -165,6 +167,7 @@
                 "-source",
                 "7",
                 "-Xlint:none",
+                "--",
                 "--sources",
                 source.toString(),
                 "--output",
@@ -206,6 +209,7 @@
             ImmutableList.of(
                 "--javacopts",
                 "-Xep:FallThrough:ERROR",
+                "--",
                 "--sources",
                 source.toString(),
                 "--source_jars",