virgl: Enable passing arrays as input to fragment shaders

This is needed to properly handle interpolateAt* when the input to be
interpolated is passed as array in the original GLSL.

Currently, the the GLSL compiler would lower selecting the correct input so
that the interpolant parameter to interpolateAt* is a temporary, and this
can not be used to create a valid shader on the host side, because here the
parameter must a shader input.

By allowing the passing the created TGSI allows to create proper GLSL.
This is related to the virglrenderer bug
  virgl/virglrenderer#74

v2: Squash the two patches handling these flags into another

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
15 jobs for !184 with add-virgl-array-input in 11 minutes and 25 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Containers Build
passed #226897
ubuntu

00:00:21

 
  Build+Test
passed #226898
autotools

00:11:01

passed #226900
meson-clang

00:09:03

passed #226906
meson-gallium-clover-llvm

00:01:32

passed #226907
meson-gallium-clover-llvm39

00:03:59

passed #226905
meson-gallium-drivers-other

00:08:46

passed #226904
meson-gallium-radeonsi

00:04:10

passed #226908
meson-gallium-st-other

00:04:36

passed #226899
meson-gallium-swr

00:09:17

passed #226903
meson-glvnd

00:05:02

passed #226902
meson-loader-classic-dri

00:04:13

passed #226901
meson-vulkan

00:01:08

passed #226910
scons-llvm

00:04:31

passed #226909
scons-nollvm

00:03:57

passed #226911
scons-swr

00:07:38