Resolves: https://github.com/spack/spack/issues/16394 (#16395)

Build problem with gcc 10.x

var/spack/repos/builtin/packages/gdbm/gdbm_gcc_10.patch

@@ -0,0 +1,11 @@
+--- gdbm-1.18.1/src/parseopt.c	2018-05-30 03:39:15.000000000 -0600
++++ gdbm-1.18.1_new/src/parseopt.c	2020-04-30 10:29:52.869582500 -0600
+@@ -255,8 +255,6 @@
+ }
+ 
+ char *parseopt_program_name;
+-char *parseopt_program_doc;
+-char *parseopt_program_args;
+ const char *program_bug_address = "<" PACKAGE_BUGREPORT ">";
+ void (*parseopt_help_hook) (FILE *stream);
+ 

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

@@ -26,6 +26,7 @@ class Gdbm(AutotoolsPackage, GNUMirrorPackage):
     version('1.9',   sha256='f85324d7de3777db167581fd5d3493d2daa3e85e195a8ae9afc05b34551b6e57')
 
     depends_on("readline")
+    patch('gdbm_gcc_10.patch', when='%gcc@10:')
 
     def configure_args(self):