Fix msvcc.sh botch

patches/msvcc-warning

@@ -32,6 +32,46 @@ Index: libffi/msvcc.sh
  md=-MD
  cl="cl"
  ml="ml"
+@@ -65,13 +65,25 @@ do
+       ml="ml64" # "$MSVC/x86_amd64/ml64"
+       shift 1
+     ;;
++    -O0)
++      args="$args -Od"
++      shift 1
++    ;;
+     -O*)
+-      args="$args $1"
++      # If we're optimizing, make sure we explicitly turn on some optimizations
++      # that are implicitly disabled by debug symbols (-Zi).
++      args="$args $1 -OPT:REF -OPT:ICF -INCREMENTAL:NO"
+       shift 1
+     ;;
+     -g)
+-      # Can't specify -RTC1 or -Zi in opt. -Gy is ok. Use -OPT:REF?
+-      args="$args -D_DEBUG -RTC1 -Zi"
++      # Enable debug symbol generation.
++      args="$args -Zi -DEBUG"
++      shift 1
++    ;;
++    -DFFI_DEBUG)
++      # Link against debug CRT and enable runtime error checks.
++      args="$args -RTC1"
++      defines="$defines $1"
+       md=-MDd
+       shift 1
+     ;;
+@@ -108,8 +120,8 @@ do
+       shift 1
+     ;;
+     -Wall)
+-      # -Wall on MSVC is overzealous. Use -W3 instead.
+-      args="$args -W3"
++      # -Wall on MSVC is overzealous, and we already build with -W3. Nothing
++      # to do here.
+       shift 1
+     ;;
+     -Werror)
 Index: libffi/ChangeLog
 ===================================================================
 --- libffi.orig/ChangeLog