tools/flock: fix compile on Alpine Linux

fixes build errors:
src/flock.c:208:34: error: 'O_NOCTTY' undeclared (first use in this function)
fd = open(filename, O_RDONLY|O_NOCTTY|O_CREAT, 0666);
src/flock.c:208:43: error: 'O_CREAT' undeclared (first use in this function)
fd = open(filename, O_RDONLY|O_NOCTTY|O_CREAT, 0666);

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@48978 3c298f89-4303-0410-b956-a3cf2f4a3e73

add a stripped down (and portable) version of flock to the host tools

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@23707 3c298f89-4303-0410-b956-a3cf2f4a3e73