build/nmk: simplify try-cc and return true/false
build/nmk: simplify try-cc and return true/false

- simplify: don't use temporary file -- use /dev/null instead
- return 'true' or 'false' -- this way we can use it inside rules
without external call to bash to compare return with 'y', see
the next patch for a use case.

Cc: Cyrill Gorcunov <7a1ea01eee6961eb1e372e3508c2670446d086f4@openvz.org>
Signed-off-by: Dmitry Safonov <5aea3f9692c8a01793193334616ae8fad2bc748a@virtuozzo.com>
Reviewed-by: Cyrill Gorcunov <7a1ea01eee6961eb1e372e3508c2670446d086f4@openvz.org>
Acked-by: Andrew Vagin <74c05afa918858348d6db8037d82fa8124870113@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@virtuozzo.com>

eabatalov/criu,eabatalov/criu,eabatalov/criu,KKoukiou/criu-remote,KKoukiou/criu-remote,eabatalov/criu,eabatalov/criu,KKoukiou/criu-remote,KKoukiou/criu-remote,eabatalov/criu,KKoukiou/criu-remote,KKoukiou/criu-remote