patch 9.1.0623: Mingw: errors when trying to delete non-existing files

Problem:  Mingw: warnings when trying to delete non-existing files
Solution: Use "rm -f" instead of "rm" to suppress errors for
          non-existing files (Ken Takata)

closes: #15350

Signed-off-by: Ken Takata <kentkt@csc.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/xxd/Make_ming.mak b/src/xxd/Make_ming.mak
index 2d32261..e621e67 100644
--- a/src/xxd/Make_ming.mak
+++ b/src/xxd/Make_ming.mak
@@ -16,7 +16,7 @@
 CFLAGS = -O2 -Wall -DWIN32 $(DEFINES)
 
 ifneq (sh.exe, $(SHELL))
-DEL = rm
+DEL = rm -f
 else
 DEL = del
 endif