[pushed] gdb: fix gnu-nat build

[Simon Marchi]

When building gnu-nat.c, we get:

      CXX    gnu-nat.o
    gnu-nat.c: In member function 'virtual void gnu_nat_target::create_inferior(const char*, const string&, char**, int)':
    gnu-nat.c:2117:13: error: 'struct inf' has no member named 'target_is_pushed'
     2117 |   if (!inf->target_is_pushed (this))
          |             ^~~~~~~~~~~~~~~~
    gnu-nat.c:2118:10: error: 'struct inf' has no member named 'push_target'
     2118 |     inf->push_target (this);
          |          ^~~~~~~~~~~

This is because of a confusion between the generic `struct inferior`
variable and the gnu-nat-specific `struct inf` variable.  Fix by
referring to `inferior`, not `inf`.

Adjust the comment on top of `struct inf` to clarify the purpose of that
type.

Co-Authored-By: Andrea Monaco <andrea.monaco@autistici.org>
Change-Id: I2fe2f7f6ef61a38d79860fd262b08835c963fc77
---
 gdb/gnu-nat.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/gdb/gnu-nat.c b/gdb/gnu-nat.c
index 54838347f947..c6cecff06867 100644
--- a/gdb/gnu-nat.c
+++ b/gdb/gnu-nat.c
@@ -149,7 +149,7 @@ struct inf_wait
     int suppress;		/* Something trivial happened.  */
   };
 
-/* The state of an inferior.  */
+/* Further Hurd-specific state of an inferior.  */
 struct inf
   {
     /* Fields describing the current inferior.  */
@@ -2108,8 +2108,8 @@ gnu_nat_target::create_inferior (const char *exec_file,
 
   inf_debug (inf, "creating inferior");
 
-  if (!inf->target_is_pushed (this))
-    inf->push_target (this);
+  if (!inferior->target_is_pushed (this))
+    inferior->push_target (this);
 
   pid = fork_inferior (exec_file, allargs, env, gnu_ptrace_me,
 		       NULL, NULL, NULL, NULL);
-- 
2.26.2