cmake: remove spaces in macro used for compiling cython code

cmake: remove spaces in macro used for compiling cython code

we are facing following FTBFS on jammy + GCC-11.2 + Cython 0.29 +
CMake 3.22:

creating /home/jenkins-build/build/workspace/ceph-api/build/lib/cython_modules/temp.linux-x86_64-3.10/home/jenkins-build/build/workspace/ceph-api/build/src/pybind/cephfs
compile options: '-I/usr/include/python3.10 -I/usr/include/python3.10 -c'
extra options: '-Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -g -fwrapv -O2 -iquote/home/jenkins-build/build/workspace/ceph-api/src/include -w -Dvoid0=dead_function(void) -D__Pyx_check_single_interpreter(ARG)=ARG ## 0 -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -g -fwrapv -O2'
cc: /home/jenkins-build/build/workspace/ceph-api/build/src/pybind/cephfs/cephfs.c
cc: warning: ##: linker input file unused because linking not done
cc: error: ##: linker input file not found: No such file or directory
cc: warning: 0: linker input file unused because linking not done
cc: error: 0: linker input file not found: No such file or directory

it seems cython is not able to escape the space in the "extra options"
anymore, so the "##" and "0" are considered as object files passed to
compiler in addition to cephfs.c.

in this change the spaces are removed to help cython to make the right
decision.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>