Use static linking on OS/2

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

configure.ac

@@ -807,7 +807,7 @@ PKG_PROG_PKG_CONFIG()
 
 dnl On some OS we need static linking
 AS_IF([test -n "${PKG_CONFIG}" ],[
-    AS_IF([test "${SYS}" = "mingw32" -o "${SYS}" = "mingwce" -o "${SYS}" = "darwin" ],[
+    AS_IF([test "${SYS}" = "mingw32" -o "${SYS}" = "mingwce" -o "${SYS}" = "darwin" -o "${SYS}" = "os2" ],[
         PKG_CONFIG="${PKG_CONFIG} --static"
     ])
 ])