slurm: add patch to allow full path lengths in --get-user-env

Fix fallout from https://github.com/NixOS/nixpkgs/pull/90041
and 5d8f61f3bf, which fixes
the crash of slurmd but "sbatch --get-user-env" did not work
properly.

pkgs/servers/computing/slurm/common-env-echo.patch

@@ -0,0 +1,13 @@
+diff --git a/src/common/env.c b/src/common/env.c
+index 987846d..73d3b3b 100644
+--- a/src/common/env.c
++++ b/src/common/env.c
+@@ -1941,7 +1941,7 @@ char **env_array_user_default(const char *username, int timeout, int mode,
+ 	char **env = NULL;
+ 	char *starttoken = "XXXXSLURMSTARTPARSINGHEREXXXX";
+ 	char *stoptoken  = "XXXXSLURMSTOPPARSINGHEREXXXXX";
+-	char cmdstr[256], *env_loc = NULL;
++	char cmdstr[MAXPATHLEN], *env_loc = NULL;
+ 	char *stepd_path = NULL;
+ 	int fd1, fd2, fildes[2], found, fval, len, rc, timeleft;
+ 	int buf_read, buf_rem, config_timeout;

pkgs/servers/computing/slurm/default.nix

@@ -22,6 +22,12 @@ stdenv.mkDerivation rec {
 
   outputs = [ "out" "dev" ];
 
+  patches = [
+    # increase string length to allow for full
+    # path of 'echo' in nix store
+    ./common-env-echo.patch
+  ];
+
   prePatch = ''
     substituteInPlace src/common/env.c \
         --replace "/bin/echo" "${coreutils}/bin/echo"