Rely on system Lua instead of shipping it

A specific version of Lua used to be required, but this is no longer the case
(I think after commit 5aae933/PR longturn#417). Use the version of Lua provided by the
system, requiring at least and prioritizing the widely available Lua 5.3.

This should fix longturn#504.

.travis.yml

@@ -22,6 +22,7 @@ jobs:
         - gettext
         - qt5-default
         - libkf5archive-dev
+        - liblua5.3-dev
         - libsqlite3-dev
         - libsdl2-mixer-dev
   - name: "ubuntu-clang"
@@ -38,6 +39,7 @@ jobs:
         - gettext
         - qt5-default
         - libkf5archive-dev
+        - liblua5.3-dev
         - libsqlite3-dev
         - libsdl2-mixer-dev
     before_script:
@@ -55,6 +57,7 @@ jobs:
           mingw-w64-x86_64-gcc
           mingw-w64-x86_64-libunwind
           mingw-w64-x86_64-readline
+          mingw-w64-x86_64-lua # There is no lua53 in MSYS, 5.4 should work...
           mingw-w64-x86_64-SDL2_mixer
           mingw-w64-x86_64-qt5
           mingw-w64-x86_64-karchive-qt5
@@ -82,6 +85,7 @@ jobs:
           - qt@5
           - kde-karchive
           - readline
+          - [email protected]
           - sqlite
           - sdl2
           - sdl2_mixer
@@ -101,6 +105,7 @@ jobs:
         - gettext
         - qt5-default
         - libkf5archive-dev
+        - liblua5.3-dev
         - libsqlite3-dev
         - libsdl2-mixer-dev
       coverity_scan:

cmake/FreecivDependencies.cmake

@@ -84,19 +84,29 @@ endif()
 
 # Lua
 #
-# Lua is not binary compatible even between minor releases. We stick to Lua 5.4.
+# Lua is not binary compatible even between minor releases. We stick to Lua 5.3.
 #
-# The tolua program is compatible with Lua 5.4, but the library may not be (eg
+# The tolua program is compatible with Lua 5.3, but the library may not be (eg
 # on Debian it's linked to Lua 5.2). We always build the library. When not
 # cross-compiling, we can also build the program. When cross-compiling, an
 # externally provided tolua program is required (or an emulator for the target
 # platform, eg qemu).
+find_package(Lua 5.3 REQUIRED)
+
+# Create an imported target since it's not created by CMake :(
+add_library(lua SHARED IMPORTED GLOBAL)
+# Get a library name for IMPORTED_LOCATION
+list(GET LUA_LIBRARIES 0 loc)
+set_target_properties(lua PROPERTIES IMPORTED_LOCATION "${loc}")
+# Link to all libs, not just the first
+target_link_libraries(lua INTERFACE "${LUA_LIBRARIES}")
+target_include_directories(lua SYSTEM INTERFACE "${LUA_INCLUDE_DIR}")
+
 if (CMAKE_CROSSCOMPILING AND NOT CMAKE_CROSSCOMPILING_EMULATOR)
   find_package(ToLuaProgram REQUIRED)
 else()
   find_package(ToLuaProgram)
 endif()
-add_subdirectory(dependencies/lua-5.4)
 add_subdirectory(dependencies/tolua-5.2) # Will build the program if not found.
 
 # backward-cpp