fontsrv: fix build on OpenBSD 5.2

R=rsc
CC=plan9port.codebot
https://codereview.appspot.com/6850108

INSTALL

@@ -45,6 +45,11 @@ rm -f config
 echo "* Compiler version:"
 9c -v 2>&1 | grep -v 'Configured with:' | grep -i version | sed 's/^/	/'
 
+if [ `uname` = OpenBSD ]; then
+       echo "* Running on OpenBSD, adjusting linker flags"
+       echo "LDFLAGS='-L/usr/X11R6/lib -pthread'" >> $PLAN9/config
+fi
+
 if [ `uname` = Linux ]; then
 	# On Linux, we use the kernel version to decide whether
 	# to use pthreads or not.  On 2.6 versions that aren't