Release notes about win32-x86-mingw cross-builds

Also a bit more cleanup of build rules.

configure/RULES_BUILD

@@ -379,9 +379,11 @@ $(INSTALL_LIB)/%$(LIB_SUFFIX): %$(LIB_SUFFIX)
 	$(ECHO) "Installing library $@"
 	@$(INSTALL_LIBRARY) -d -m $(LIB_PERMISSIONS) $< $(INSTALL_LIB)
 
+ifneq ($(LIB_SUFFIX),$(DLLSTUB_SUFFIX))
 $(INSTALL_LIB)/%$(DLLSTUB_SUFFIX): %$(DLLSTUB_SUFFIX)
 	$(ECHO) "Installing DLL stub library $@"
 	@$(INSTALL_LIBRARY) -d -m $(LIB_PERMISSIONS) $< $(INSTALL_LIB)
+endif # SUFFIX
 
 $(INSTALL_SHRLIBS): $(INSTALL_SHRLIB)/%: %
 	$(ECHO) "Installing shared library $@"

documentation/RELEASE_NOTES.html

@@ -15,6 +15,15 @@ EPICS Base 3.15.0.x releases are not intended for use in production systems.</p>
 <h2 align="center">Changes between 3.14.x and 3.15.0.x</h2>
 <!-- Insert new items immediately below here ... -->
 
+<h3>Cross-builds targeting win32-x86-mingw</h3>
+
+<p>Some Linux distributions now package the MinGW cross-compiler which makes it
+possible to cross-build the win32-x86-mingw target from a linux-x86 host. Build
+configuration files for this combination are now included; adjust the settings
+in configure/os/CONFIG_SITE.linux-x86.win32-x86-mingw and add win32-x86-mingw to
+the CROSS_COMPILER_TARGET_ARCHS variable in configure/CONFIG_SITE or in
+configure/os/CONFIG_SITE.linux-x86.Common.</p>
+
 <h3>Architecture win32-x86-cygwin Removed</h3>
 
 <p>The ability to compile non-cygwin binaries using the Cygwin build tools is no

src/ioc/db/RULES

@@ -11,8 +11,6 @@
 
 # This is a Makefile fragment, see src/ioc/Makefile.
 
-# $(filter-out $(STATIC_SRCS),$(dbCore_SRCS)) : $(COMMON_DIR)/dbCommon.h
-
 dbCommon.h$(DEP): $(IOCDIR)/db/dbCommonRecord.dbd
 	@$(RM) $@
 	@$(DBTORECORDTYPEH) -D -I ../db -o $(COMMONDEP_TARGET) $< > $@