meson: Add cygwin to list of platforms requiring explicit driver sele…

…ction

The default values for --dri-drivers, --gallium-drivers and --vulkan-drivers
aren't specified for cygwin, either.

XXX: maybe we should do this right??

meson.build

@@ -94,7 +94,7 @@ with_dri_swrast = false
 _drivers = get_option('dri-drivers')
 if _drivers == 'auto'
   # TODO: PPC, Sparc
-  if not ['darwin', 'windows'].contains(host_machine.system())
+  if not ['darwin', 'windows', 'cygwin'].contains(host_machine.system())
     if ['x86', 'x86_64'].contains(host_machine.cpu_family())
       _drivers = 'i915,i965,r100,r200,nouveau'
     else
@@ -127,7 +127,7 @@ with_gallium_etnaviv = false
 with_gallium_imx = false
 _drivers = get_option('gallium-drivers')
 if _drivers == 'auto'
-  if not ['darwin', 'windows'].contains(host_machine.system())
+  if not ['darwin', 'windows', 'cygwin'].contains(host_machine.system())
     # TODO: PPC, Sparc
     if ['x86', 'x86_64'].contains(host_machine.cpu_family())
       _drivers = 'radeonsi,nouveau,swrast'
@@ -290,7 +290,7 @@ with_amd_vk = false
 with_any_vk = false
 _vulkan_drivers = get_option('vulkan-drivers')
 if _vulkan_drivers == 'auto'
-  if not ['darwin', 'windows'].contains(host_machine.system())
+  if not ['darwin', 'windows', 'cygwin'].contains(host_machine.system())
     if host_machine.cpu_family().startswith('x86')
       _vulkan_drivers = 'amd,intel'
     else