missing .la generated files

Hello,

When I cross-compile mesa-9.1.3, I do:
$ scons platform=windows toolchain=crossmingw machine=x86 mesagdi libgl-gdi

Then I copy:
* all the .a generated files to /usr/i686-pc-mingw32/lib directory
* all the .dll generated files to /usr/i686-pc-mingw32/bin directory

But I think something is missing.
Indeed, I have not .la generated files.

For example, when I compile SDL, I have .a, .dll and .la files.
With Mesa, the .la files are missing.

These .la files are important because they are useful when using libtool.

For example, I am unable to cross-compile freeglut because libtool does not find this missing file.
In fact, I am not sure it is the reason, but I guess.

Do you see how to install correctly mesa-9.1.3 (i.e. with the .la files) ?
Also, is there an automatic way to install (instead of manually copy the files) ?

Thank you.
Best regards.