turn off epoxy egl support by default and enable only when gtk3 is enabled

to build on the festering baseline on which gtk3 is disabled

Change-Id: I6c074382590fc60ae8572fbde225679e4309494e

configure.ac

@@ -10431,7 +10431,6 @@ elif test $_os = WINNT; then
 else
     if test "$USING_X11" = TRUE; then
         AC_CHECK_LIB(GL, glBegin, [:], AC_MSG_ERROR([libGL required.]))
-        AC_CHECK_LIB(EGL, eglMakeCurrent, [:], AC_MSG_ERROR([libEGL required.]))
         ENABLE_OPENGL_TRANSITIONS=TRUE
         AC_DEFINE(HAVE_FEATURE_OPENGL,1)
         ENABLE_OPENGL_CANVAS=TRUE

external/epoxy/Library_epoxy.mk

@@ -55,9 +55,20 @@ else
 $(eval $(call gb_Library_add_generated_cobjects,epoxy,\
 	UnpackedTarball/epoxy/src/dispatch_glx \
 	UnpackedTarball/epoxy/src/glx_generated_dispatch \
+))
+ifeq ($(ENABLE_GTK3),TRUE)
+$(eval $(call gb_Library_add_cflags,epoxy,\
+	-DPLATFORM_HAS_EGL=1 \
+))
+$(eval $(call gb_Library_add_generated_cobjects,epoxy,\
 	UnpackedTarball/epoxy/src/dispatch_egl \
 	UnpackedTarball/epoxy/src/egl_generated_dispatch \
 ))
+else
+$(eval $(call gb_Library_add_cflags,epoxy,\
+	-DPLATFORM_HAS_EGL=0 \
+))
+endif
 endif
 
 # vim: set noet sw=4 ts=4:

external/epoxy/UnpackedTarball_epoxy.mk

@@ -15,6 +15,7 @@ $(eval $(call gb_UnpackedTarball_set_patchlevel,epoxy,0))
 
 $(eval $(call gb_UnpackedTarball_add_patches,epoxy, \
     external/epoxy/epoxy.windows.api.patch \
+    external/epoxy/epoxy.noegl.by.default.patch \
 ))
 
 # vim: set noet sw=4 ts=4:

external/epoxy/epoxy.noegl.by.default.patch

+--- src/dispatch_common.h
++++ src/dispatch_common.h
+@@ -39,7 +39,7 @@
+ #define PLATFORM_HAS_WGL 0
+ #define EPOXY_IMPORTEXPORT
+ #else
+-#define PLATFORM_HAS_EGL 1
++
+ #define PLATFORM_HAS_GLX 1
+ #define PLATFORM_HAS_WGL 0
+ #define EPOXY_IMPORTEXPORT