olsr: fix build

Pass TARGET_CONFIGURE_OPTS in the environment rather than as make arguments,
so the olsr build system can append to CFLAGS / LDFLAGS - Otherwise build
fails when the wrong linker flags are used to create the plugin .so's.

Also pass ARCH, so the olsr build system choses the right libdir / PIC
settings for the target, rather than for the host.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>