Make ruby a optional dependency

test/meson.build

@@ -48,6 +48,7 @@ subdir('cmp_max_used_bits')
 test_args = '-Wno-missing-declarations' # The test runner generator does not generate header files
 fs = import('fs')
 
+if ruby.found()
   foreach test : test_cases
     test_src = test[0]
     test_description = test[1]
@@ -71,5 +72,6 @@ foreach test : test_cases
 
     test(test_description, test_exe)
   endforeach
+endif
 
 subdir('bench')

test/tools/meson.build

+ruby = find_program('ruby', required : false)
+if ruby.found()
   generate_test_runner = find_program('generate_test_runner.rb')
-test_runner_generator = generator(
-  generate_test_runner,
+  test_runner_generator = generator(generate_test_runner,
     output: ['@BASENAME@_Runner.c'],
     arguments: ['@INPUT@', '@OUTPUT@']
   )
+endif
 
 # add checkpatch syntax-check target
 checkpatch = find_program('checkpatch.pl', 'checkpatch', required : false)