Fix build on OS X; ld needs 'install_name', not 'soname'

configure

@@ -357,7 +357,12 @@ if test "$COMPILER" = "suncc"; then
 	PTHREAD_CFLAGS="-mt -lpthread"
 elif test "$COMPILER" = "gcc"; then
 	LD=$CC
-	LDFLAGS="-shared -fPIC -Wl,-soname,libck.so.$VERSION_MAJOR $LDFLAGS"
+	if test "$SYSTEM" = "darwin"; then
+		CC_WL_OPT="-install_name"
+	else
+		CC_WL_OPT="-soname"
+	fi
+	LDFLAGS="-shared -fPIC -Wl,$CC_WL_OPT,libck.so.$VERSION_MAJOR $LDFLAGS"
 	CFLAGS="-D_XOPEN_SOURCE=600 -D_BSD_SOURCE -std=gnu99 -pedantic -Wall -W -Wundef -Wendif-labels -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-align -Wwrite-strings -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wdisabled-optimization -fstrict-aliasing -O2 -pipe -Wno-parentheses $CFLAGS"
 	PTHREAD_CFLAGS="-pthread"
 else