fixincludes: don't abort() on access failure [PR103306]

Some distro may ship dangling symlinks in include directories, triggers
the access failure.  Skip it and continue to next header instead of
being to panic.

Restore to old behavior before r12-5234 but without resurrecting the
problematic getcwd() call, by using the environment variable "INPUT"
exported by fixinc.sh.

Tested on x86_64-linux-gnu, with a dangling symlink intentionally
injected into /usr/include.

fixincludes/

	PR bootstrap/103306
	* fixincl.c (process): Don't call abort().

fixincludes/fixincl.c

@@ -1352,10 +1352,19 @@ process (void)
 
   if (access (pz_curr_file, R_OK) != 0)
     {
-      /* Some really strange error happened.  */
-      fprintf (stderr, "Cannot access %s: %s\n", pz_curr_file,
+      /* It may happens if for e. g. the distro ships some broken symlinks
+	 in /usr/include.  */
+
+      /* "INPUT" is exported in fixinc.sh, which is the pwd where fixincl
+	 runs.  It's used instead of getcwd to avoid allocating a buffer
+	 with unknown length.  */
+      const char *cwd = getenv ("INPUT");
+      if (!cwd)
+	cwd = "the working directory";
+
+      fprintf (stderr, "Cannot access %s from %s: %s\n", pz_curr_file, cwd,
 	       xstrerror (errno));
-      abort ();
+      return;
     }
 
   pz_curr_data = load_file (pz_curr_file);