meson: extract out variable for nir_algebraic.py

Also needed in freedreno/ir3.

Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

src/compiler/nir/meson.build

@@ -193,6 +193,8 @@ libnir = static_library(
   build_by_default : false,
 )
 
+nir_algebraic_py = files('nir_algebraic.py')
+
 if with_tests
   nir_control_flow_test = executable(
     'nir_control_flow_test',

src/intel/compiler/meson.build

@@ -122,7 +122,7 @@ brw_nir_trig = custom_target(
   output : 'brw_nir_trig_workarounds.c',
   command : [prog_python2, '@INPUT@', '-p',
              join_paths(meson.source_root(), 'src/compiler/nir/')],
-  depend_files : files('../../compiler/nir/nir_algebraic.py'),
+  depend_files : nir_algebraic_py,
   capture : true,
 )