ncl: Fix buffer overflow in ymake-filter (#5357)

Fixes a problem in ymake-filter: The line buffer is currently hardcoded to be
2048 bytes large but some Makefiles contain lines longer than that. This
caused the Makefiles to sometimes not be generated, consequently failing parts
of the build.

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

@@ -43,6 +43,8 @@ class Ncl(Package):
     patch('spack_ncl.patch')
     # Make ncl compile with hdf5 1.10
     patch('hdf5.patch')
+    # ymake-filter's buffer may overflow
+    patch('ymake-filter.patch')
 
     # This installation script is implemented according to this manual:
     # http://www.ncl.ucar.edu/Download/build_from_src.shtml

var/spack/repos/builtin/packages/ncl/ymake-filter.patch

@@ -0,0 +1,33 @@
+--- ncl_ncarg-6.4.0/config/ymake-filter.c.orig	2017-02-23 20:11:55.000000000 +0100
++++ ncl_ncarg-6.4.0/config/ymake-filter.c	2017-09-13 14:52:34.800989229 +0200
+@@ -150,13 +150,29 @@
+ getcppline()
+ {
+ 	int		c;
+-	static char	buf[2048];
++	static int	s = 2048;
++	static char	*buf = NULL;
+ 	char 		*p;
+ 
++	if (buf == NULL)
++	{
++		buf = malloc(s);
++	}
++
+ 	p = buf;
+ 
+ 	do
+ 	{
++		if (p >= buf + s)
++		{
++			char* old = buf;
++
++			/* Need to increase the size of buf. */
++			s += 1024;
++			buf = realloc(buf, s);
++			p = buf + (p - old);
++		}
++
+ 		switch(c = getchar())
+ 		{
+ 			/*