Define luabins as a valid subproject

meson.build

@@ -292,13 +292,9 @@ else
 endif
 
 if not deps.contains(luajit)
-    luajit_sp = subproject('luajit')
-    luajit_inc = luajit_sp.get_variable('src_inc')
-    deps += luajit_sp.get_variable('luajit_dep')
-else
-    luajit_inc = include_directories(luajit.get_variable('includedir'))
+    deps += subproject('luajit').get_variable('luajit_dep')
 endif
-subdir('subprojects/luabins/src')
+deps += subproject('luabins').get_variable('luabins_dep')
 
 dep_gl = dependency('gl', required: false)
 if not dep_gl.found()
@@ -342,7 +338,7 @@ aegisub_cpp_pch = ['src/include/agi_pre.h']
 aegisub_c_pch = ['src/include/agi_pre_c.h']
 
 aegisub = executable('aegisub', aegisub_src, version_h, acconf,
-                     link_with: [libresrc, libluabins, libaegisub],
+                     link_with: [libresrc, libaegisub],
                      include_directories: [libaegisub_inc, libresrc_inc, version_inc, deps_inc, include_directories('src')],
                      cpp_pch: aegisub_cpp_pch,
                      c_pch: aegisub_c_pch,

subprojects/luabins/meson.build

@@ -0,0 +1,13 @@
+project('luabins', ['c'])
+luabins_src = files(
+    'src/fwrite.c',
+    'src/load.c',
+    'src/luabins.c',
+    'src/luainternals.c',
+    'src/savebuffer.c',
+    'src/save.c',
+    'src/write.c',
+)
+
+luabins = static_library('luabins', luabins_src, dependencies: dependency('luajit'))
+luabins_dep = declare_dependency(link_with: luabins)

subprojects/luabins/src/meson.build

@@ -1,11 +0,0 @@
-luabins_src = files(
-    'fwrite.c',
-    'load.c',
-    'luabins.c',
-    'luainternals.c',
-    'savebuffer.c',
-    'save.c',
-    'write.c',
-)
-
-libluabins = static_library('luabins', luabins_src, include_directories: luajit_inc)