build(lib_install_dir): added lib_install_dir option

this option is useful for wheel builds

src/constants/meson.build

@@ -5,12 +5,14 @@ const_sources = files(
 
 
 # Define the libconst library so it can be linked against by other parts of the build system
+fourdst_component_libdir = get_option('lib_install_dir') != '' ? get_option('lib_install_dir') : get_option('libdir')
 libconst = library('const',
     const_sources, 
     include_directories: include_directories('include'),
     cpp_args: ['-fvisibility=default'],
     dependencies: [const_data_dep],
-    install : true)
+    install : true,
+    install_dir: fourdst_component_libdir)
 
 const_dep = declare_dependency(
     include_directories: include_directories('include'),