RFR: JDK-8151402: Allow template files from closed and open repos

[Gary Adams]

Here is the proposed update to the GensrcMisc.gmk makefile.

If a closed repos makefile is present, let it provide an alternate 
closed location for
the template files. If it does not exist attempt to use the template 
from the open repos
location.

This change will allow the template files to be located in closed or 
open repos as needed
by the target cross compilation platform.


diff --git a/make/gensrc/GensrcMisc.gmk b/make/gensrc/GensrcMisc.gmk
--- a/make/gensrc/GensrcMisc.gmk
+++ b/make/gensrc/GensrcMisc.gmk
@@ -22,6 +22,7 @@
  # or visit www.oracle.com if you need additional information or have any
  # questions.
  #
+$(eval $(call IncludeCustomExtension, jdk, gensrc/GensrcMisc.gmk))

  ##########################################################################################
  # Install the launcher name, release version string, full version
@@ -58,7 +59,9 @@
      OUTPUT_DIR := $(GENSRC_SOR_BIN), \
      PROGRAM := genSocketOptionRegistry))

-SOR_PREGEN_FILE := 
$(JDK_TOPDIR)/src/java.base/$(OPENJDK_TARGET_OS)/classes/sun/nio/ch/SocketOptionRegistry-$(OPENJDK_TARGET_OS)-$(OPENJDK_TARGET_CPU_ARCH).java.template
+ifeq ($(wildcard $(SOR_PREGEN_FILE)), )
+  SOR_PREGEN_FILE := 
$(JDK_TOPDIR)/src/java.base/$(OPENJDK_TARGET_OS)/classes/sun/nio/ch/SocketOptionRegistry-$(OPENJDK_TARGET_OS)-$(OPENJDK_TARGET_CPU_ARCH).java.template
+endif

  ifeq ($(wildcard $(SOR_PREGEN_FILE)), )
$(SUPPORT_OUTPUTDIR)/gensrc/java.base/sun/nio/ch/SocketOptionRegistry.java: 
$(BUILD_GENSRC_SOR_EXE)
@@ -94,7 +97,9 @@
        OUTPUT_DIR := $(GENSRC_UC_BIN), \
        PROGRAM := genUnixConstants))

-  UC_PREGEN_FILE := 
$(JDK_TOPDIR)/src/java.base/$(OPENJDK_TARGET_OS)/classes/sun/nio/fs/UnixConstants-$(OPENJDK_TARGET_OS)-$(OPENJDK_TARGET_CPU_ARCH).java.template
+  ifeq ($(wildcard $(UC_PREGEN_FILE)), )
+    UC_PREGEN_FILE := 
$(JDK_TOPDIR)/src/java.base/$(OPENJDK_TARGET_OS)/classes/sun/nio/fs/UnixConstants-$(OPENJDK_TARGET_OS)-$(OPENJDK_TARGET_CPU_ARCH).java.template
+  endif

    ifeq ($(wildcard $(UC_PREGEN_FILE)), )
$(SUPPORT_OUTPUTDIR)/gensrc/java.base/sun/nio/fs/UnixConstants.java: 
$(BUILD_GENSRC_UC_EXE)