configure.ac: relax linux OS detection

Not all linux hosts match the *-pc-linux-gnu wildcard, causing build
failures for older glibc versions where we need to link with -lrt for
clock_gettime - E.G.:

 - arm-unknown-linux-musleabihf
 - powerpc-unknown-linux-gnuspe
 - bfin-linux-linux-uclibc
 ..

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Erik de Castro Lopo <erikd@mega-nerd.com>
1 file changed