meson: Fix TODO for missing dl_iterate_phdr function

This function is required for both the Intel "Anvil" vulkan driver and
the i965 GL driver. Error out if either of those is enabled but this
function isn't found.

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
diff --git a/meson.build b/meson.build
index 23ed42e..f844289 100644
--- a/meson.build
+++ b/meson.build
@@ -660,8 +660,10 @@
 
 if cc.has_function('dl_iterate_phdr')
   pre_args += '-DHAVE_DL_ITERATE_PHDR'
-else
-  # TODO: this is required for vulkan
+elif with_intel_vk
+  error('Intel "Anvil" Vulkan driver requires the dl_iterate_phdr function')
+elif with_dri_i965 and get_option('shader-cache')
+  error('Intel i965 GL driver requires dl_iterate_phdr when built with shader caching.')
 endif
 
 # Determine whether or not the rt library is needed for time functions