Use $(command) instead of `command`, it's POSIX, clearer and already used.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@8586 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

configure

@@ -750,7 +750,7 @@ mmi="default"
 bigendian="no"
 
 # OS
-targetos=`tolower \` uname -s\` `
+targetos=$(tolower $(uname -s))
 beos_netserver="no"
 os2="no"
 wince="no"