subversion: fix build problem when sysroot contains '-D' or '-I'

If sysroot contains '-D' or '-I' characters, the SVN_NEON_INCLUDES and
the corresponding CFLAGS will not get the correct value.

This will cause build failures.

This patch fixes the above problem.

[YOCTO #5458]

(From OE-Core master rev: 7078397ef39de43244fca7e24683b2a83913cbbf)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>