Add RULES_COMMON

This adds new make targets 'PRINT.<var-name>' and 'show-makefiles'
which are useful for debugging build problems.

configure/RULES_ARCHS

@@ -90,6 +90,4 @@ realclean:
 .PHONY : $(BUILD_ARCHS) rebuild archsCommonClean
 .PHONY : $(ACTIONS) clean realclean archclean host all
 
-#  User specific rules
+include $(CONFIG)/RULES_COMMON
-#
--include $(HOME)/configure/RULES_USER

configure/RULES_BUILD

@@ -530,5 +530,7 @@ $(INSTALL_TEMPLATES_SUBDIR)/%: %
 .PHONY: runtests tapfiles clean-tests test-results junitfiles
 .PHONY: checkRelease warnRelease noCheckRelease FORCE
 
+include $(CONFIG)/RULES_COMMON
+
 endif # BASE_RULES_BUILD
 #	EOF RULES_BUILD

configure/RULES_COMMON

@@ -0,0 +1,33 @@
+#*************************************************************************
+# Copyright (c) 2018 UChicago Argonne LLC, as Operator of Argonne
+#     National Laboratory.
+# EPICS BASE is distributed subject to a Software License Agreement found
+# in the file LICENSE that is included with this distribution.
+#*************************************************************************
+
+# These rules show the set of Makefiles, config files and
+# rules files loaded by GNUmake.
+
+SHOW_MAKEFILES = $(MAKEFILE_LIST:%=show-makefile.%)
+show-makefiles: $(SHOW_MAKEFILES)
+
+# The sort prevents warnings about duplicate targets:
+$(sort $(SHOW_MAKEFILES)): show-makefile.%:
+	@echo "    $(@:show-makefile.%=%)"
+
+.PHONY: show-makefiles show-makefile.%
+
+# These rules support printing a Makefile variable values.
+# Many variables are only set inside an O.<arch> build directory.
+#   make PRINT.T_A
+
+PRINT_Var = $(@:PRINT.%=%)
+PRINT.%:
+	@echo "$(PRINT_Var) = '$($(PRINT_Var))'"
+
+.PHONY: PRINT PRINT.%
+
+
+#  User specific rules
+#
+-include $(HOME)/configure/RULES_USER

configure/RULES_DIRS

@@ -92,7 +92,4 @@ $(ARCHS) $(ACTIONS) $(actionArchTargets) :%: \
 .PHONY : $(dirActionArchTargets)
 .PHONY : $(actionArchTargets)
 
-
+include $(CONFIG)/RULES_COMMON
-#  User specific rules
-#
--include $(HOME)/configure/RULES_USER

configure/RULES_FILE_TYPE

@@ -67,7 +67,3 @@ file_type_clean:
 	@$(RM) $(foreach type, $(FILE_TYPE), $($(type)))
 
 .PHONY : file_type_clean
-
-#  User specific rules
-#
--include $(HOME)/configure/RULES_USER

documentation/RELEASE_NOTES.html

@@ -19,6 +19,22 @@
 
 -->
 
+<h3>GNUmake targets for debugging</h3>
+
+<p>Some additional build rules have been added to help debug configuration
+problems with the build system. Run <tt>make show-makefiles</tt> to get a sorted
+list of all the files that the build system includes when building in the
+current directory.</p>
+
+<p>A new pattern rule for <tt>PRINT.%</tt> can be used to show the value of any
+GNUmake variable for the current build directory (make sure you are in the right
+directory though, many variables are only set when inside the
+<tt>O.<i>arch</i></tt> build directory). For example <tt>make PRINT.T_A</tt>
+will display the build target architecture name from inside a
+<tt>O.<i>arch</i></tt> directory but the variable will be empty from an
+application top or src directory. <tt>make PRINT.EPICS_BASE</tt> will show the
+path to Base from any EPICS application directory though.</p>
+
 <h3>Propagate PUTF across Asynchronous record processing</h3>
 
 <p>The IOC contains a mechanism involving the PUTF and RPRO fields of each