source code for the nsinstall contained in moztools

[tradiate]

I'm working on Windows. I've downloaded the mozilla tree, and a binary
version of moztools which is compatible with Windows, and have gotten
Firefox to build just fine. I then put the mozilla source tree under
Perforce source control (prior to my hacking on it). This means that
files in my local working copy of the tree are R/O unless I've checked
them out. The fact that files are R/O now causes the build to fail.
Here's why:

moztools/bin/nsinstall is attempting to copy some files around (from
location in soiurce tree down into the build target area), and if it
has done it previously, the target location now contains a R/O file so
the copy attempt fails with 'access denied' errors.

To get around this problem, I'd like to make a local update to
nsinstall (e.g. add something like a -f option to cause a force write)
and then use that option in the makefiles. Problem is, I'm not sure
how to go about building nsinstall on Windows. I see nsinstall.c
sitting in the mozilla/config dir, but 1) I'm not sure this is indeed
the source for the nsinstall I'm using from moztools, and 2) if it is
the correct source, I'm not sure how to build it for Windows.

Can anyone enlighten me?