package/win32: Force libtool build when using llvm-mingw

The libtool in extras/tools has additional patches that are needed to
build with llvm-mingw.

(cherry picked from commit f88b10e49d7fb04c360ec0ad13f94f9d5dc6d4e3)
9 jobs for !2 with llvm-bare/1 in 45 minutes and 53 seconds (queued for 3 seconds)
latest merge request
Name Stage Failure
failed
snap Build
Priming fixup-vulkan-icd-paths 
Determining the version from the project repo (version-script).
The version-script produced no output
package.mak:2: recipe for target 'snap' failed
make: *** [snap] Error 2
Running after script...
$ export VLC_CONTRIB_SHA="$(extras/ci/get-contrib-sha.sh)"
$ mv extras/package/snap/parts/vlc/build/contrib/vlc-contrib-*.tar.bz2 contrib/vlc-contrib-${TRIPLET}-${VLC_CONTRIB_SHA}.tar.bz2 2>/dev/null || true
ERROR: Job failed: exit code 1