sci-visualization/grace: fix implicit-in-configure

Closes: https://bugs.gentoo.org/942342
Signed-off-by: Alfredo Tupone <tupone@gentoo.org>

sci-visualization/grace/files/grace-5.1.25_p18-config.patch

@@ -0,0 +1,10 @@
+--- a/configure	2026-04-24 14:49:53.519758443 +0200
++++ b/configure	2026-04-24 14:51:11.453860825 +0200
+@@ -7800,6 +7800,7 @@
+ /* end confdefs.h.  */
+ 
+ #include <string.h>
++#include <stdlib.h>
+ #include <t1lib.h>
+       int main(void) {
+         char *vlib;

sci-visualization/grace/grace-5.1.25_p18.ebuild

@@ -42,6 +42,7 @@ PATCHES=(
 	# Fix C99 compat (from Fedora); included in debian "source-hardening"???
 	#"${FILESDIR}"/${PN}-c99.patch
 	"${FILESDIR}"/${PN}-configure-c99.patch
+	"${FILESDIR}"/${P}-config.patch
 )
 
 pkg_setup() {