8062635: Enable custom CompileJavaClasses.gmk

Reviewed-by: erikj

make/CompileJavaClasses.gmk

@@ -36,6 +36,11 @@ JARS :=
 EXFILES :=
 EXCLUDES :=
 
+##########################################################################################
+# Include the corresponding custom file, if present.
+
+-include $(CUSTOM_MAKE_DIR)/CompileJavaClasses.gmk
+
 ##########################################################################################
 
 EXCLUDES += com/sun/pept \
@@ -53,7 +58,7 @@ endif
 
 ifndef OPENJDK
   # There exists two versions of these files...
-  EXFILES := $(JDK_TOPDIR)/src/share/classes/javax/crypto/JarVerifier.java
+  EXFILES += $(JDK_TOPDIR)/src/share/classes/javax/crypto/JarVerifier.java
   EXFILES += $(JDK_TOPDIR)/src/share/classes/sun/management/ExtendedPlatformComponent.java
 
   ifeq ($(OPENJDK_TARGET_OS), windows)