Trying out multi-threaded FFTW

Anyone know how I can get extra linker options passed in for FFTW3F
during configure?
The Gnu Radio build system is, well, fiendishly complicated, and doing
the obvious:

FFTW3F_LIBS='-lfftw3f_threads -lfftw3f -lm ’ ./configure

Provokes an error:

=== configuring in usrp2/firmware (/home/mleech/gnuradio/usrp2/firmware)
configure: running /bin/sh ./configure.gnu --disable-option-checking
‘–prefix=/usr/local’ ‘FFTW3F_LIBS=-lfftw3f_threads -lfftw3f -lm ’
–cache-file=/dev/null --srcdir=.
configure: error: unrecognized option: -lfftw3f
Try `./configure --help’ for more information.
configure: error: ./configure.gnu failed for usrp2/firmware

Principal Investigator
Shirleys Bay Radio Astronomy Consortium