lz4: fix host build with glibc older than 2.17

glibc before 2.17 require the -lrt linker option for clock_gettime(). We
do not support pre 2.17 glibc for the target anymore, but there are
still host platforms with these versions. Add upstream patch to skip use
of clock_gettime() with older glibc versions.

Should fix:
http://autobuild.buildroot.net/results/bc5/bc5d6447ab16a61d9dcf56723106f0b107826ef4/
http://autobuild.buildroot.net/results/7dd/7dd47bef902845a0f7803f1a6c702ec154855858/
http://autobuild.buildroot.net/results/952/9523dbc767dc325befabeb9240c4009e78779c7d/



Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>