nco: Add patch to fix invalid conversion from char to char* (#5102)

This patch is needed to be able to build nco with GCC 7.

var/spack/repos/builtin/packages/nco/NUL-0-NULL.patch

@@ -0,0 +1,51 @@
+From fec59e92795bfac5779d09cd5d96f10cd1c3e6af Mon Sep 17 00:00:00 2001
+From: Charlie Zender <zender@uci.edu>
+Date: Thu, 1 Jun 2017 20:18:02 -0700
+Subject: [PATCH] Patch for NUL = '\0' != NULL errors in ncap2 supplied by
+ Manfred Schwarb
+
+---
+ src/nco++/fmc_all_cls.cc | 8 ++++----
+ 2 files changed, 6 insertions(+), 4 deletions(-)
+
+diff --git a/src/nco++/fmc_all_cls.cc b/src/nco++/fmc_all_cls.cc
+index 3cccc17..79e3240 100644
+--- a/src/nco++/fmc_all_cls.cc
++++ b/src/nco++/fmc_all_cls.cc
+@@ -4796,14 +4796,14 @@ var_sct *vlist_cls::push_fnd(bool &is_mtd, std::vector<RefAST> &vtr_args, fmc_cl
+   {
+      case PATOI: 
+        {          
+-         char *pend='\0';
++         char *pend=NULL;
+          nco_int iout;
+          iout=0; 
+ 
+ 	 // allows whites space prefix & suffix                                                                                                                                
+          iout=(nco_int)std::strtol(buffer,&pend,10);
+ 
+-         if( pend !=buffer  && (*pend=='\0'|| *pend==' ') )
++         if(pend != buffer && (*pend == '\0'|| *pend == ' '))
+             ierr=0;
+          else
+             ierr=errno;
+@@ -4817,14 +4817,14 @@ var_sct *vlist_cls::push_fnd(bool &is_mtd, std::vector<RefAST> &vtr_args, fmc_cl
+ 
+      case PATOL: 
+        {          
+-         char *pend='\0';
++         char *pend=NULL;
+          nco_int64 lout;
+          lout=0; 
+ 
+ 	      // allows whites space prefix & suffix
+          lout=(nco_int64)std::strtoll(buffer,&pend,10);
+ 
+-         if( pend !=buffer  && (*pend=='\0'|| *pend==' ') )
++         if( pend !=buffer && (*pend == '\0' || *pend == ' '))
+             ierr=0;
+          else
+ 	        ierr=errno;
+-- 
+2.7.4
+

var/spack/repos/builtin/packages/nco/package.py

@@ -41,6 +41,9 @@ class Nco(AutotoolsPackage):
     version('4.6.1', 'ef43cc989229c2790a9094bd84728fd8')
     version('4.5.5', '9f1f1cb149ad6407c5a03c20122223ce')
 
+    # https://github.com/nco/nco/issues/43
+    patch('NUL-0-NULL.patch')
+
     variant('doc', default=False, description='Build/install NCO TexInfo-based documentation')
 
     # See "Compilation Requirements" at: