libcap-ng: cannot be built with nios2 CS 2014.05 toolchain

Fixes:
http://autobuild.buildroot.net/results/d13/d136f763ca3389cdc6a404db7a4fc0cd18329955/
http://autobuild.buildroot.net/results/e00/e002e2a3bd52a3cc3b0d06625de61315d86de524/
http://autobuild.buildroot.net/results/bba/bba9f7130315c9d97cc060a73663276d0fa2c1b3/
http://autobuild.buildroot.net/results/fc7/fc7bc050ef769716dedb0ad81a51e33a12deec47/



And many more.

Building libcap-ng with that toolchain triggers an internal compiler /
assembler bug, so blacklist that combination and propagate to the reverse
dependencies.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>