mksh: add option for static linking.

srcpkgs/mksh/template

@@ -1,7 +1,7 @@
 # Template file for 'mksh'
 pkgname=mksh
 version=R50e
-revision=2
+revision=3
 wrksrc=mksh
 build_pie=yes
 register_shell="/bin/mksh"
@@ -12,7 +12,13 @@ license="MirOS"
 distfiles="https://www.mirbsd.org/MirOS/dist/mir/mksh/$pkgname-$version.tgz"
 checksum=ad3c148769d08cf934a96be2837599ba9db355f38a8f49c7bc8876b80d2e08da
 
+build_options="static"
+
 do_build() {
+	if [ "$build_option_static" ]; then
+		CFLAGS+=" -static"
+		LDFLAGS+=" -static"
+	fi
 	sh ./Build.sh -r -c lto
 }