glsl: add missing support for explicit components in interface blocks

glsl: add missing support for explicit components in interface blocks

From the ARB_enhanced_layouts spec:

   "As with input layout qualifiers, all shaders except compute shaders
   allow *location* layout qualifiers on output variable declarations,
   output block declarations, and output block member declarations.  Of
   these, variables and block members (but not blocks) additionally
   allow the *component* layout qualifier."

We previously had compile tests in piglit to make sure this was not a
compile error but no execution tests.

Fixes: d99a040bbf2c ("i965: enable ARB_enhanced_layouts for gen8+")

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10763>