unixodbc: fix clean-build compilation

For host compilation, the configure-generated config.h from the target
compilation is used in place of the host-generated file.  When the
target package is compiled with clean-build, that file is gone.  This
saves the file under $(STAGING_DIR), and fetch it from there.

Signed-off-by: Eneas U de Queiroz <cote2004-github@yahoo.com>

libs/unixodbc/Makefile

@@ -97,6 +97,8 @@ endef
 define Build/InstallDev
 	$(INSTALL_DIR) $(1)/usr/include
 	$(CP) $(PKG_INSTALL_DIR)/$(STAGING_DIR)/usr/include/*.h $(1)/usr/include/
+	# Save autoconf config.h file for host build
+	$(CP) $(PKG_BUILD_DIR)/config.h $(1)/usr/include/unixodbc_ac_config.h
 	$(INSTALL_DIR) $(1)/usr/lib
 	$(CP) $(PKG_INSTALL_DIR)/usr/lib/* $(1)/usr/lib/
 	$(INSTALL_DIR) $(1)/etc
@@ -131,7 +133,8 @@ endef
 
 define Host/Configure
 	$(call Host/Configure/Default)
-	cp $(PKG_BUILD_DIR)/config.h $(HOST_BUILD_DIR)
+	# copy target autoconf config.h file for host build
+	cp $(STAGING_DIR)/usr/include/unixodbc_ac_config.h $(HOST_BUILD_DIR)
 	sed -i -e 's!\(LIB_PREFIX \).*$$$$!\1"$(STAGING_DIR)/usr/lib"!' $(HOST_BUILD_DIR)/config.h
 	cp $(PKG_BUILD_DIR)/unixodbc_conf.h $(HOST_BUILD_DIR)
 endef