Add an option to the MSVC makefile to enable treating warnings as errors.

FossilOrigin-Name: 6a378c29b43d61313ca9daa599e59d8eeeed9a27

autoconf/Makefile.msc

@@ -24,6 +24,13 @@ TOP = .
 USE_FULLWARN = 0
 !ENDIF
 
+# Set this non-0 to enable treating warnings as errors (-WX, etc) when
+# compiling.
+#
+!IFNDEF USE_FATAL_WARN
+USE_FATAL_WARN = 0
+!ENDIF
+
 # Set this non-0 to enable full runtime error checks (-RTC1, etc).  This
 # has no effect if (any) optimizations are enabled.
 #
@@ -454,6 +461,12 @@ TCC = $(CC) -nologo -W4 -DINCLUDE_MSVC_H=1 $(CCOPTS) $(TCCOPTS)
 TCC = $(CC) -nologo -W3 $(CCOPTS) $(TCCOPTS)
 !ENDIF
 
+# Check if warnings should be treated as errors when compiling.
+#
+!IF $(USE_FATAL_WARN)!=0
+TCC = $(TCC) -WX
+!ENDIF
+
 TCC = $(TCC) -DSQLITE_OS_WIN=1 -I. -I$(TOP) -fp:precise
 RCC = $(RC) -DSQLITE_OS_WIN=1 -I. -I$(TOP) $(RCOPTS) $(RCCOPTS)