Improve meson build.

-Add all required packages as wrap dependencies
-Move source lsitnings to separate files
-Proper dependencies declarations
-Set global D compiler arguments
-Add few asserts
-Add test exe
-Other small improvements

Tested with dmd with betterC, demos executable has to be run from 'demos' directory to properly load assets.

meson.build

@@ -1,42 +1,29 @@
-project('DECS', 'd')
-
-src = [
-	'source/bubel/ecs/atomic.d',
-	'source/bubel/ecs/attributes.d',
-	'source/bubel/ecs/block_allocator.d',
-	'source/bubel/ecs/core.d',
-	'source/bubel/ecs/entity.d',
-	'source/bubel/ecs/events.d',
-	'source/bubel/ecs/hash_map.d',
-	'source/bubel/ecs/id_manager.d',
-	'source/bubel/ecs/manager.d',
-	'source/bubel/ecs/package.d',
-	'source/bubel/ecs/simple_vector.d',
-	'source/bubel/ecs/std.d',
-	'source/bubel/ecs/system.d',
-	'source/bubel/ecs/traits.d',
-	'source/bubel/ecs/vector.d'
-]
-
-tests_src = [
-	'tests/tests.d'
-]
+project('decs', 'd', version : '0.5.0')
 
+# Options
 betterC_opt = get_option('betterC')
 BuildDemos_opt = get_option('BuildDemos')
 LTO_otp = get_option('LTO')
 
-comp = meson.get_compiler('d')
+summary('betterC enabled', betterC_opt)
+summary('build demos', BuildDemos_opt)
+summary('LTO enabled', LTO_otp)
 
-comp_id = comp.get_id()
+meson_minimum_version = '>=0.57.1'
+assert(meson.version().version_compare(meson_minimum_version), 'Newer verson of meson required, current version: @0@, required: @1@'.format(meson.version(), meson_minimum_version))
 
+# Files
+src = files()
+subdir('source')
+
+inc = include_directories('source/')
+
+# Arguments
 args = []
 link_args = []
 
-if comp_id == 'gcc'
-	args += '-pthread'
-	link_args += '-pthread'
-endif
+comp = meson.get_compiler('d')
+comp_id = comp.get_id()
 
 if LTO_otp
 	if comp_id == 'gcc'
@@ -46,7 +33,7 @@ if LTO_otp
 		args += '-flto=thin'
 		link_args += '-flto=thin'
 	else
-		message('LTO don\'t work with DMD')
+		assert(false, 'Compiler "@0@" doesn\'t support LTO'.format(comp_id))
 	endif
 endif
 
@@ -60,16 +47,27 @@ if betterC_opt
 	endif
 endif
 
-inc = include_directories('source/')
-tests_inc = include_directories('source/')
+add_global_arguments(args, language : 'd')
+add_global_link_arguments(link_args, language : 'd')
 
-ecs_lib = library('ecs', src, include_directories : [tests_inc, inc], d_args: args, link_args: link_args)
+# Dependencies
+threads_dep = dependency('threads')
 
-executable('tests', tests_src, include_directories : [tests_inc, inc], d_args: args, link_args: link_args, link_with: ecs_lib)
+ecs_lib = library('decs',
+	src,
+	include_directories : [inc],
+)
 
-bubel_ecs_dep = declare_dependency(include_directories : [inc], link_with : ecs_lib)
+decs_dep = declare_dependency(
+	include_directories : [inc],
+	link_with : ecs_lib,
+	dependencies : threads_dep,	
+)
 
+# Tests
+subdir('tests')
+
+# Demos
 if BuildDemos_opt
-	subdir('demos/utils')
 	subdir('demos')
 endif