Fix GPI-2 and enable TAGASPI

The rdma-core driver.h include is no longer installed:

 56dd87acd2

So ibv_read_sysfs_file() is not defined. As the symbols is still
distributed, we simply add the missing prototype manually.

Similarly, the gaspi_get_system_mem() function is not available from the
gaspi public headers, so we define it in the max_mem.c test.

Fixes: rarias/bscpkgs#7
Reviewed-by: Aleix Boné <abonerib@bsc.es>
Tested-by: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>

pkgs/gpi-2/default.nix

@@ -34,6 +34,8 @@ stdenv.mkDerivation rec {
 
   enableParallelBuilding = true;
 
+  patches = [ ./rdma-core.patch ./max-mem.patch ];
+
   preConfigure = ''
     patchShebangs autogen.sh
     ./autogen.sh

pkgs/gpi-2/max-mem.patch

@@ -0,0 +1,10 @@
+--- a/tests/tests/segments/max_mem.c	2025-09-12 13:30:53.449353591 +0200
++++ b/tests/tests/segments/max_mem.c	2025-09-12 13:33:49.750352401 +0200
+@@ -1,5 +1,7 @@
+ #include <test_utils.h>
+ 
++gaspi_size_t gaspi_get_system_mem (void);
++
+ /* Test allocates 45% of system memory and creates a segment that
+    large or if several ranks per node exist, divided among that
+    number */

pkgs/gpi-2/rdma-core.patch

@@ -0,0 +1,12 @@
+--- a/src/devices/ib/GPI2_IB.h	2025-09-12 13:25:31.564181121 +0200
++++ b/src/devices/ib/GPI2_IB.h	2025-09-12 13:24:49.105422150 +0200
+@@ -26,6 +26,9 @@ along with GPI-2. If not, see <http://ww
+ 
+ #include "GPI2_Dev.h"
+ 
++/* Missing prototype as driver.h is now private */
++int ibv_read_sysfs_file(const char *dir, const char *file, char *buf, size_t size);
++
+ #define GASPI_GID_INDEX   (0)
+ #define PORT_LINK_UP      (5)
+ #define MAX_INLINE_BYTES  (128)