patch 8.2.1583: MS-Windows: cannot easily measure code coverage

Problem:    MS-Windows: cannot easily measure code coverage.
Solution:   Add the COVERAGE option. (Ken Takata, closes #6842)
diff --git a/src/Make_cyg_ming.mak b/src/Make_cyg_ming.mak
index db0513f..5fc0833 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -38,6 +38,9 @@
 # set to yes to create a mapfile
 #MAP=yes
 
+# set to yes to measure code coverage
+COVERAGE=no
+
 # set to SIZE for size, SPEED for speed, MAXSPEED for maximum optimization
 OPTIMIZE=MAXSPEED
 
@@ -700,6 +703,11 @@
 LFLAGS += -s
 endif
 
+ifeq ($(COVERAGE),yes)
+CFLAGS += --coverage
+LFLAGS += --coverage
+endif
+
 LIB = -lkernel32 -luser32 -lgdi32 -ladvapi32 -lcomdlg32 -lcomctl32 -lnetapi32 -lversion
 GUIOBJ =  $(OUTDIR)/gui.o $(OUTDIR)/gui_w32.o $(OUTDIR)/gui_beval.o
 CUIOBJ = $(OUTDIR)/iscygpty.o
@@ -938,6 +946,9 @@
  ifneq ($(DEBUG),yes)
 EXELFLAGS += -s
  endif
+ ifeq ($(COVERAGE),yes)
+EXELFLAGS += --coverage
+ endif
 DEFINES += $(DEF_GUI) -DVIMDLL
 OBJ += $(GUIOBJ) $(CUIOBJ)
 OUTDIR = dobj$(DEBUG_SUFFIX)$(MZSCHEME_SUFFIX)$(ARCH)