Getting an error when compiling with "--with-threads=flavor"

[Compro P. <com...@gm...>]

Compiling without MT is fine and there are no extras. But when using
"./configure --with-threads=flavour" I have to manually run `make
CFLAGS+="-lpthread"`. But still it doesn't compile. It complains about not
having package FFI. For further information I have given the output of
`make CFLAGS+="-lpthread"` below which I have ran from the project root:

cd src && /usr/bin/make all
make[1]: Entering directory
'/run/media/compro/eb7b593c-d20e-4393-be34-3b108921f50e/home/compro/Dropbox/programs/hg/clisp/src'
./lisp.run -B . -N locale -E UTF-8 -Emisc 1:1 -Epathname 1:1 -norc -m 2MW
-M halfcompiled.mem -q -c foreign1.lisp -o ./
;; Compiling file
/run/media/compro/eb7b593c-d20e-4393-be34-3b108921f50e/home/compro/Dropbox/programs/hg/clisp/src/foreign1.lisp
...
*** - SYSTEM::%FIND-PACKAGE: There is no package with name "FFI"

0 errors, 0 warnings
make[1]: *** [Makefile:1687: foreign1.fas] Error 1
make[1]: Leaving directory
'/run/media/compro/eb7b593c-d20e-4393-be34-3b108921f50e/home/compro/Dropbox/programs/hg/clisp/src'
make: *** [Makefile:16: all] Error 2