use /mingw/bin for copying dlls when building on Windows with msys2

The old path was /usr/local/bin, but I think Hans was manually adding the dlls there. If not we can use an ifdef to set this specifically for use with msys2

packages/win32_inno/Makefile

@@ -62,7 +62,8 @@ prebuilt_install:
 #
 #==============================================================================#
 
-bin_src = /usr/local/bin
+#bin_src = /usr/local/bin
+bin_src = /mingw/bin
 system32 = /c/WINDOWS/system32
 lib_install:
 # ultimately, the DLLs should be installed in %SystemRoot%\system32 by