User: Fix Windows build

User/Makefile

@@ -48,23 +48,33 @@ ifeq ($(WERROR),1)
 	CFLAGS += -Werror
 endif
 
-ifeq ($(shell echo 'int a;' | "${CC}" -Wno-unused-parameter -x c -c - -o /dev/null 2>&1),)
+#
+# On Windows, output file cannot be null.
+# Ref: https://github.com/msys2/MINGW-packages/issues/10520
+#
+ifeq ($(DIST),Windows)
+	OUT_BIN := /tmp/windows_out
+else
+	OUT_BIN := /dev/null
+endif
+
+ifeq ($(shell echo 'int a;' | "${CC}" -Wno-unused-parameter -x c -c - -o "${OUT_BIN}" 2>&1),)
 	CFLAGS += -Wno-unused-parameter
 endif
 
-ifeq ($(shell echo 'int a;' | "${CC}" -Wno-implicit-fallthrough -x c -c - -o /dev/null 2>&1),)
+ifeq ($(shell echo 'int a;' | "${CC}" -Wno-implicit-fallthrough -x c -c - -o "${OUT_BIN}" 2>&1),)
 	CFLAGS += -Wno-implicit-fallthrough
 endif
 
-ifeq ($(shell echo 'int a;' | "${CC}" -Wno-strict-aliasing -x c -c - -o /dev/null 2>&1),)
+ifeq ($(shell echo 'int a;' | "${CC}" -Wno-strict-aliasing -x c -c - -o "${OUT_BIN}" 2>&1),)
 	CFLAGS += -Wno-strict-aliasing
 endif
 
-ifeq ($(shell echo 'int a;' | "${CC}" -Wno-address -x c -c - -o /dev/null 2>&1),)
+ifeq ($(shell echo 'int a;' | "${CC}" -Wno-address -x c -c - -o "${OUT_BIN}" 2>&1),)
 	CFLAGS += -Wno-address
 endif
 
-ifeq ($(shell echo 'int a;' | "${CC}" -Wno-stringop-overflow -x c -c - -o /dev/null 2>&1),)
+ifeq ($(shell echo 'int a;' | "${CC}" -Wno-stringop-overflow -x c -c - -o "${OUT_BIN}" 2>&1),)
 	CFLAGS += -Wno-stringop-overflow
 endif