meson: Fix checking options build-bits.

On FreeBSD run --auto-features=disabled -Dbuild-libblkid=enabled
-Dprogram-tests=false

builded bin/bits

Sponsored by: Future Crew, LLC

meson.build

@@ -1215,11 +1215,12 @@ exe = executable(
   include_directories : includes,
   link_with : lib_common,
   install_dir : usrbin_exec_dir,
-  install : true)
+  install : opt,
+  build_by_default : opt)
 if opt and not is_disabler(exe)
-exes += exe
-manadocs += ['text-utils/bits.1.adoc']
-bashcompletions += ['bits']
+  exes += exe
+  manadocs += ['text-utils/bits.1.adoc']
+  bashcompletions += ['bits']
 endif
 
 opt = not get_option('build-col').require(is_glibc).disabled()