iris: Enable ARB_gl_spirv and ARB_spirv_extensions

This will also "unlock" OpenGL 4.6 for Iris!

v2: Also enable PIPE_CAP_GL_SPIRV_VARIABLE_POINTERS.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com> [v1]
22 jobs for !1743 with r/iris-spirv in 19 minutes and 45 seconds (queued for 19 seconds)
detached
Status Job ID Name Coverage
  Containers Build
passed #590427
debian

00:00:20

 
  Build+Test
passed #590436
meson-arm64

00:01:42

passed #590435
meson-armhf

00:02:27

passed #590430
meson-clang

00:09:06

passed #590433
meson-clover

00:10:20

passed #590437
meson-i386

00:04:01

passed #590428
meson-main

00:11:33

passed #590429
meson-swr-glvnd

00:05:34

passed #590434
meson-vulkan

00:03:10

passed #590439
scons-llvm

00:03:58

passed #590438
scons-nollvm

00:03:02

passed #590431
scons-swr

00:05:04

passed #590432
scons-win64

00:09:17

 
  Test
passed #590440
test-llvmpipe-gles2 1/4

00:03:35

passed #590441
test-llvmpipe-gles2 2/4

00:03:55

passed #590442
test-llvmpipe-gles2 3/4

00:03:44

passed #590443
test-llvmpipe-gles2 4/4

00:03:52

passed #590444
test-softpipe-gles2 1/4

00:01:33

passed #590445
test-softpipe-gles2 2/4

00:01:34

passed #590446
test-softpipe-gles2 3/4

00:01:24

passed #590447
test-softpipe-gles2 4/4

00:01:32

passed #590448
test-softpipe-gles3-limited

00:03:59