Makefile, ich_descriptors_tool/Makefile: unify behavior

ich_descriptors_tool/Makefile: have the same behavior as the main
flashrom Makefile
  - only set gcc explicit on MinGW HOST_OS
  - don't fallback to gcc if CC was not set
  - set CFLAGS and EXEC_SUFFIX for TARGET_OS, not for HOST_OS

Change-Id: I353c3de250167994a4aea1edfef57d839e900d78
Signed-off-by: Thomas Heijligen <thomas.heijligen@secunet.com>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/58468
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72250
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/Makefile b/Makefile
index 59c75d6..9d8bb78 100644
--- a/Makefile
+++ b/Makefile
@@ -829,7 +829,7 @@
 
 all: hwlibs features $(PROGRAM)$(EXEC_SUFFIX) $(PROGRAM).8
 ifeq ($(ARCH), x86)
-	@+$(MAKE) -C util/ich_descriptors_tool/ TARGET_OS=$(TARGET_OS) EXEC_SUFFIX=$(EXEC_SUFFIX)
+	@+$(MAKE) -C util/ich_descriptors_tool/ HOST_OS=$(HOST_OS) TARGET_OS=$(TARGET_OS)
 endif
 
 $(PROGRAM)$(EXEC_SUFFIX): $(OBJS)