Update README.md (#820)

For cygwin/MSVC build, CXXCPP is also needed to pass configure checks

diff --git a/README.md b/README.md
index 5ddaada4e1cf9892748389707750297198a82249..d8d97705422dddf8c7877416b84d72e3b6eb502f 100644 (file)
--- a/README.md
+++ b/README.md
@@ -158,7 +158,7 @@ It's also possible to build libffi on Windows platforms with
 Microsoft's Visual C++ compiler.  In this case, use the msvcc.sh
 wrapper script during configuration like so:
 
-    path/to/configure CC=path/to/msvcc.sh CXX=path/to/msvcc.sh LD=link CPP="cl -nologo -EP" CPPFLAGS="-DFFI_BUILDING_DLL"
+    path/to/configure CC=path/to/msvcc.sh CXX=path/to/msvcc.sh LD=link CPP="cl -nologo -EP" CXXCPP="cl -nologo -EP" CPPFLAGS="-DFFI_BUILDING_DLL"
 
 For 64-bit Windows builds, use ``CC="path/to/msvcc.sh -m64"`` and
 ``CXX="path/to/msvcc.sh -m64"``.  You may also need to specify