flatcc: fix build with gcc 8

flatcc: fix build with gcc 8

gcc 8 enables a strncpy() warning. This breaks the build of flatcc that
enables -Werror. Add upstream patch fixing the issue.

Fixes:
http://autobuild.buildroot.net/results/0e3/0e3a959855fad5899db184f7d2c960c89df03672/
http://autobuild.buildroot.net/results/d2c/d2c03bc253bdf135b0f31f3d1e6fd33f7d37d64b/
http://autobuild.buildroot.net/results/163/1636ec6ddad92add95f42451d941156451c6d936/

Cc: Joel Carlson <JoelsonCarl@gmail.com>
Cc: Mikkel Fahnøe Jørgensen <mikkel@dvide.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Joel Carlson <JoelsonCarl@gmail.com>
Tested-by: Joel Carlson <JoelsonCarl@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>