gnu: tensorflow-lite: Update to 2.12.1.

* gnu/packages/algebra.scm (eigen-for-tensorflow-lite): Remove variable.
* gnu/packages/machine-learning.scm (tensorflow-lite): Update to 2.12.1
[arguments]<configure-flags>: Turn on GPU and RUY use; Use cmake to
find packages already in Guix as dependencies for absl-cpp, eigen,
flatbuffer, neon2ssl, cpuinfo, ruy.
[arguments]<phases>: Remove operations setting up absl-cpp, eigen, ruy,
and neon2ssl as native inouts as now we use Guix's packages of these
as dependencies. Do default build phase.
Add steps to install C shared library and benchmark_model tool.
[inputs]: Add cpuinfo, eigen, fp16, mesa-header, opencl,
pthreadpool, ruy, vulkan and xnnpack as explicit inputs.
[native-inputs]: Remove local setup of neon2ssl and ruy
as we now use Guix's packages of these as explicit dependencies.
* gnu/packages/serialization.scm (flatbuffers-next-shared): New variable,
flatbuffers-next built with -fPIC as needed by tensorflow-lite.

Signed-off-by: Ricardo Wurmus <rekado@elephly.net>

gnu/packages/serialization.scm

@@ -811,6 +811,17 @@ game development and other performance-critical applications.")
                (base32
                 "1z3a6l8g2y53i5xzraswfs2i0i3kk52zv7nzc2q3fgisbyiri3pz"))))))
 
+(define-public flatbuffers-next-shared
+  (package
+    (inherit flatbuffers-next)
+    (name "flatbuffers-shared")
+    (version "23.1.21")
+    (arguments
+     (substitute-keyword-arguments (package-arguments flatbuffers-next)
+       ((#:configure-flags  flags)
+        ;; Compile with -fPIC, needed for shared lib.
+        #~(cons "-DFLATBUFFERS_CXX_FLAGS=-fPIC" #$flags))))))
+
 (define-public python-feather-format
   (package
     (name "python-feather-format")