package/bison: fix parallel build issue

package/bison: fix parallel build issue

Following the bump of Bison to 3.4.1 in commit
d3c2f33543b91670f8ead627ec7975142b9e6b5a, the build started failing on
autobuilders using a fairly old version of make (3.81). The failure is
caused by a parallel build problem in examples/c/reccalc/.

Fixing it is not trivial, and would require autoreconf, which then
fails due to help2man being missing. So for the time being, simply
disable parallel build on bison.

The issue has been reported to the bug-bison@ mailing list, but the
e-mail doesn't appear yet in the mailing list archives.

Fixes:

  http://autobuild.buildroot.net/results/856/8568bcef944096f2c21470d36f02b520989af5eb/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>