[arch] Can't build wlan-ng26 against 2.6.18-rc4 kernel

[Tom K]

I've installed tpowa's 2.6.18-rc4 testing kernel from here:

http://www.archlinux.org/~tpowa/2.6.18/

and I'm trying to build wlan-ng26 against it. It aborts, as follows:

cp Modules.symvers ../prism2/driver
cp: cannot stat `Modules.symvers': No such file or directory
make[2]: *** [default] Error 1
make[2]: Leaving directory 
`/home/tomk/builds/wlan-ng26/src/linux-wlan-ng-0.2.3/src/p80211'
make[1]: *** [all] Error 2
make[1]: Leaving directory 
`/home/tomk/builds/wlan-ng26/src/linux-wlan-ng-0.2.3/src'
make: *** [all] Error 2

During a successful build e.g. against the 2.6.17 kernel, 
Modules.symvers is created in the src/p80211 directory. I don't know 
exactly why it isn't created under 2.6.18-rc4, but there are errors 
during wlan-ng26's configure stage that probably have something to do 
with it:

Linux source directory [/lib/modules/2.6.18-rc4-ARCH/build]
get_version.c: In function 'main':
get_version.c:5: error: 'UTS_RELEASE' undeclared (first use in this 
function)
get_version.c:5: error: (Each undeclared identifier is reported only once
get_version.c:5: error: for each function it appears in.)
make[1]: *** [get_version] Error 1
./Configure: line 246: scripts/make.opts: No such file or directory

The kernel source tree is version .
Kernel 2.5/2.6 support is highly experimental.

./Configure: line 305: [: too many arguments

./Configure: line 343: scripts/make.opts: No such file or directory

I expect that the failure to identify the kernel version from the 
2.6.18-rc4 source tree is particularly relevant. Looking into that, I 
found that the testing kernel does not include a .kernelrelease file - 
would that be relevant here?

Any clues gratefully accepted.
TIA.