feature/pgtk af1e279 073/100: Restore support for terminal only emacs in PGTK (add --with-pgtk)

[Yuuki Harano]

branch: feature/pgtk
commit af1e279c1530a2df76136a466bccddadcdd9bc7b
Author: Jeff Walsh <fejfighter@gmail.com>
Commit: Jeff Walsh <jeff.walsh@drtusers-MacBook-Pro.local>

    Restore support for terminal only emacs in PGTK (add --with-pgtk)
    
    * configure.ac: add "--with-pgtk" switch for building pgtk terminal
    support.
    Adjust X11 window system tests to no clobber pgtk preferences
---
 configure.ac | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index 16f7ef0..66f9b7e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -468,6 +468,7 @@ AC_ARG_WITH([ns],[AS_HELP_STRING([--with-ns],
 [use Nextstep (macOS Cocoa or GNUstep) windowing system.
 On by default on macOS.])],[],[with_ns=maybe])
 OPTION_DEFAULT_OFF([w32], [use native MS Windows GUI in a Cygwin build])
+OPTION_DEFAULT_OFF([pgtk], [use pure GTK build without reliance on X libs 
(Wayland support) - Experimental])
 
 OPTION_DEFAULT_ON([gpm],[don't use -lgpm for mouse support on a GNU/Linux 
console])
 OPTION_DEFAULT_ON([dbus],[don't compile with D-Bus support])
@@ -1830,11 +1831,15 @@ AC_SUBST(AUTO_DEPEND)
 ## window-system-specific substs.
 
 window_system=none
+
+if test "${with_pgtk}" = "yes"; then
+  window_system=pgtk
+fi
+
+
 AC_PATH_X
-if test "$no_x" != yes; then
+if test "$no_x" != yes && test "${with_pgtk}" != "yes"; then
   window_system=x11
-else
-  window_system=pgtk
 fi
 
 LD_SWITCH_X_SITE_RPATH=