meson: Don't add extra values to shader-cache

We're trying to move to using a feature here, adding more values breaks
that.

Fixes: 5de56937a3d009659076dc67de6a57379fc7a31b
       ("disk_cache: build option for disabled-by-default")

Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7699>
(cherry picked from commit 7ca4a478ad307e3e706e86b2786929a6a3b7dff8)
diff --git a/meson.build b/meson.build
index d1c3541..b0107a2 100644
--- a/meson.build
+++ b/meson.build
@@ -906,12 +906,12 @@
 endif
 if _shader_cache != 'disabled'
   if host_machine.system() == 'windows'
-    if ['enabled', 'default-disabled'].contains(_shader_cache)
+    if _shader_cache == 'enabled'
       error('Shader Cache does not currently work on Windows')
     endif
   else
     pre_args += '-DENABLE_SHADER_CACHE'
-    if _shader_cache == 'default-disabled'
+    if not get_option('shader-cache-default')
       pre_args += '-DSHADER_CACHE_DISABLE_BY_DEFAULT'
     endif
     with_shader_cache = true
@@ -1782,7 +1782,7 @@
       endif
     endif
   endif
-  if (with_egl or 
+  if (with_egl or
       with_dri3 or (
       with_gallium_vdpau or with_gallium_xvmc or with_gallium_xa or
       with_gallium_omx != 'disabled'))