rc: fix cross build, enable PIE.

srcpkgs/rc/template

@@ -1,7 +1,8 @@
 # Template file for 'rc'
 pkgname=rc
 version=1.7.2
-revision=1
+revision=2
+build_pie=1
 build_style=gnu-configure
 configure_args="ac_cv_sys_restartable_syscalls=no
  $(vopt_if readline --with-edit=gnu)
@@ -25,3 +26,10 @@ pre_configure() {
 		LDFLAGS+=" -static"
 	fi
 }
+
+pre_build() {
+	if [ "$CROSS_BUILD" ]; then
+		make CC="$BUILD_CC" CFLAGS="$BUILD_CFLAGS" LIBS= LDFLAGS= \
+			sigmsgs.c sigmsgs.h statval.h
+	fi
+}