gallium: handle drirc disable_glsl_line_continuations option

NOTE: This is a candidate for the 9.1 branch

Signed-off-by: Vadim Girlin <vadimgirlin@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

src/mesa/state_tracker/st_extensions.c

@@ -714,6 +714,9 @@ void st_init_extensions(struct st_context *st)
    if (st->options.force_glsl_extensions_warn)
 	   ctx->Const.ForceGLSLExtensionsWarn = 1;
 
+   if (st->options.disable_glsl_line_continuations)
+	   ctx->Const.DisableGLSLLineContinuations = 1;
+
    ctx->Const.MinMapBufferAlignment =
       screen->get_param(screen, PIPE_CAP_MIN_MAP_BUFFER_ALIGNMENT);
    if (ctx->Const.MinMapBufferAlignment >= 64) {