Otherwise JNAetor enry.jar binding generation on
CI using `make all` results in
```
/home/travis/build/bzz/enry/java/shared/libenry.h:8:0:
error: File not found: stddef.h in
. /usr/include /usr/local/include /usr/include/c++/4.8.4 /usr/include/c++/4.8.4/tr1
```
Signed-off-by: Alexander Bezzubov <bzz@apache.org>