fftw: Remove hardcoded sysroot into binaries

FFTW_CC is added to image via version.o and its CC + CFLAGS however CC
in OE containes --syroot compiler option which encodes buildpaths into
binary, therefore remove this option from FFTW_CC in config.h

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-support/fftw/fftw_3.3.10.bb

@@ -55,6 +55,7 @@ do_configure() {
 do_compile() {
     for lib in fftw fftwl fftwf; do
         cd ${WORKDIR}/build-$lib
+        sed -i -e 's|${TOOLCHAIN_OPTIONS}||g' config.h
         autotools_do_compile
     done
 }