meson: build libmesa_gallium

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
diff --git a/meson.build b/meson.build
index ff2ce55..0ffa280 100644
--- a/meson.build
+++ b/meson.build
@@ -90,12 +90,17 @@
   with_dri = true
 endif
 
-dep_libdrm_intel = []
-if with_dri_i915
-  dep_libdrm_intel = dependency('libdrm_intel', version : '>= 2.4.75')
+with_gallium = false
+with_gallium_radeonsi = false
+_drivers = get_option('gallium-drivers')
+if _drivers != ''
+  _split = _drivers.split(',')
+  with_gallium_radeonsi = _split.contains('radeonsi')
+  with_gallium = true
+  with_dri = true
 endif
 
-if not with_dri
+if not (with_dri or with_gallium)
   with_gles1 = false
   with_gles2 = false
   with_opengl = false
@@ -103,12 +108,14 @@
   with_shared_glapi = false
 endif
 
+dep_libdrm_intel = []
+if with_dri_i915
+  dep_libdrm_intel = dependency('libdrm_intel', version : '>= 2.4.75')
+endif
+
 # TODO: other OSes
 with_dri_platform = 'drm'
 
-with_gallium = false
-# TODO: gallium drivers
-
 # TODO: conditionalize libdrm requirement
 dep_libdrm = dependency('libdrm', version : '>= 2.4.75')
 pre_args += '-DHAVE_LIBDRM'
@@ -207,7 +214,7 @@
   endif
 endif
 
-if with_dri # TODO: or gallium
+if with_dri or with_gallium
   if with_glx == 'disabled' # TODO: or egl
     error('building dri or gallium drivers require at least one window system')
   endif
@@ -564,8 +571,6 @@
 # TODO: flags for xa, egl, gbm, nin, xvmc, vdpau, omx, va, opencl,
 #       gallium-tests,
 
-# TODO: gallium drivers
-
 # TODO: symbol mangling
 
 # TODO: egl configuration