configure.ac: remove unused sdkdir=$(pkg-config...) statement

The sdkdir variable isn't use, so remove the statement.
Acked-by: Dan Nicholson <dbn.lists@gmail.com>
Signed-off-by: Gaetan Nadon <memsize@videotron.ca>

configure.ac

@@ -63,7 +63,6 @@ XORG_DRIVER_CHECK_EXT(XV, videoproto)
 
 # Checks for pkg-config packages
 PKG_CHECK_MODULES(XORG, [xorg-server >= 1.0.99.901 xproto fontsproto $REQUIRED_MODULES])
-sdkdir=$(pkg-config --variable=sdkdir xorg-server)
 
 save_CFLAGS="$CFLAGS"
 CFLAGS="$XORG_CFLAGS"