cboard: assume that /dev/ptmx always available & works

Fix for on-device builds.

packages/cboard/configure.patch

@@ -1,7 +1,23 @@
-diff -u -r ../cboard-0.7.3/configure ./configure
+diff -uNr cboard-0.7.5/configure cboard-0.7.5.mod/configure
---- ../cboard-0.7.3/configure	2015-01-18 12:26:31.000000000 -0500
+--- cboard-0.7.5/configure	2018-09-27 17:48:24.000000000 +0300
-+++ ./configure	2015-07-11 06:51:31.092218872 -0400
++++ cboard-0.7.5.mod/configure	2019-08-16 14:05:44.294565834 +0300
-@@ -11484,40 +11484,7 @@
+@@ -12194,13 +12194,8 @@
+ 
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking for Unix98 pty support" >&5
+ $as_echo_n "checking for Unix98 pty support... " >&6; }
+-if test -c "/dev/ptmx"; then
+-    have_ptmx=yes
+-else
+-    have_ptmx=no
+-fi
+-
+-ptmx_works=no
++have_ptmx=yes
++ptmx_works=yes
+ 
+ if test "x$have_ptmx" = "xyes"; then
+     ac_ext=c
+@@ -12210,40 +12205,7 @@
  ac_compiler_gnu=$ac_cv_c_compiler_gnu
  
      if test "$cross_compiling" = yes; then :