From news from lxde blog here so i try to compile this on my archlinux 64bit… like usual u need to download the libfm and pcmanfm source and extract it…

Then you must be install the libfm first.... if you have libfm from repo please remove it, to keep system clean...
so here how i compile libfm :
$./configure --prefix=/usr --enable-udisks
$make
$sudo make install

a bit different on pcmanfm
$./configure --prefix=/usr
$make LDFLAGS+="-lm"
$sudo make install