Hello,
I have attached to this message a patch that modifies the code in configure.bat that parses the --cflags and --ldflags options to support parameters that include the = character. Note that this functionality depends on command extensions. Configure.bat now attempts to enable command extensions and displays a warning message if they could not be enabled. If configure.bat could not enable command extensions the old parsing code is used that does not support parameters that include the = character.
Note that the technique I used requires that any --cflags or --ldflags parameter that includes the = character be enclosed in quotes to prevent the = character from being interpreted as a separator. The quotes are striped when the parameter is processed. Note the the parameter does not need to be enclosed in quotes if it does not include the = character.
This patch includes changes to the nt/INSTALL file provided by Eli Zaretskii.
I tested these changes on Windows 2000, Windows XP, and Windows 7. I also tested in the case in which command extensions are disabled via the registry on Windows XP. Note that in the case in which command extensions are disabled the setlocal command successfully enabled them. I do not know of a case in which configure.bat will fall back to the old parsing code (perhaps Windows NT, I do not know because I do not have a PC running Windows NT to use for testing).