commit fec515a7ac9991a0ee91068fda046b54b191155e
Author: fanquake <fanquake@gmail.com>
Date:   Wed Jul 27 15:52:37 2022 +0100

    build: respect CFLAGS in makefile.mingw
    
    Similar to the other Makefile.

    Cherry-pick of https://github.com/miniupnp/miniupnp/pull/619.

diff --git a/Makefile.mingw b/Makefile.mingw
index 2bff7bd..88430d2 100644
--- a/Makefile.mingw
+++ b/Makefile.mingw
@@ -19,7 +19,7 @@ else
 RM = rm -f
 endif
 #CFLAGS = -Wall -g -DDEBUG -D_WIN32_WINNT=0X501
-CFLAGS = -Wall -W -Wstrict-prototypes -Os -DNDEBUG -D_WIN32_WINNT=0X501
+CFLAGS ?= -Wall -W -Wstrict-prototypes -Os -DNDEBUG -D_WIN32_WINNT=0X501
 LDLIBS = -lws2_32 -liphlpapi
 # -lwsock32
 # -liphlpapi is needed for GetBestRoute() and GetIpAddrTable()