main: buffer array variables can have array size of 0 if they are unsized

From ARB_program_query_interface:

  For the property ARRAY_SIZE, a single integer identifying the number of
  active array elements of an active variable is written to <params>. The
  array size returned is in units of the type associated with the property
  TYPE. For active variables not corresponding to an array of basic types,
  the value one is written to <params>. If the variable is a shader
  storage block member in an array with no declared size, the value zero
  is written to <params>.

v2:
- Unsized arrays of arrays have an array size different than zero

v3:
- Arrays and unsized arrays will have an array_stride > 0. Use it
  instead of is_unsized_array flag (Timothy).

Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Reviewed-by: Timothy Arceri <t_arceri@yahoo.com.au>

src/mesa/main/shader_query.cpp

@@ -1308,8 +1308,15 @@ _mesa_program_resource_prop(struct gl_shader_program *shProg,
       switch (res->Type) {
       case GL_UNIFORM:
       case GL_BUFFER_VARIABLE:
+         /* Test if a buffer variable is an array or an unsized array.
+          * Unsized arrays return zero as array size.
+          */
+         if (RESOURCE_UNI(res)->is_shader_storage &&
+             RESOURCE_UNI(res)->array_stride > 0)
+            *val = RESOURCE_UNI(res)->array_elements;
+         else
             *val = MAX2(RESOURCE_UNI(res)->array_elements, 1);
-            return 1;
+         return 1;
       case GL_PROGRAM_INPUT:
       case GL_PROGRAM_OUTPUT:
          *val = MAX2(_mesa_program_resource_array_size(res), 1);