rockspec: define directories with headers and lib

Sometimes one need to compile a luzer module with a non-system Lua
library and headers, for which the LUA_LIBRARIES and
LUA_INCLUDE_DIR CMake options are used. The patch adds variables
for the rockspec to set these options via environment variables:
LUA_LIBRARIES and LUA_INCLUDE_DIR.

Needed for google/oss-fuzz#14610

Author: ligurio

CMakeLists.txt

@@ -16,6 +16,13 @@ endif()
 set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 include(SetClangRTLib)
 
+if(NOT "${CMAKE_LUA_LIBRARIES}" STREQUAL "")
+  set(LUA_LIBRARIES "${CMAKE_LUA_LIBRARIES}")
+endif()
+if(NOT "${CMAKE_LUA_INCLUDE_DIR}" STREQUAL "")
+  set(LUA_INCLUDE_DIR "${CMAKE_LUA_INCLUDE_DIR}")
+endif()
+
 if(LUA_INCLUDE_DIR AND LUA_LIBRARIES)
   # When a path to a Lua library is passed outside, we should
   # mimic a real CMake library to don't break code that depends on

luzer-scm-1.rockspec

@@ -26,6 +26,8 @@ build = {
     -- https://github.com/luarocks/luarocks/blob/7ed653f010671b3a7245be9adcc70068c049ef68/docs/config_file_format.md#config-file-format
     -- luacheck: pop
     variables = {
+        CMAKE_LUA_INCLUDE_DIR = "$(LUA_INCLUDE_DIR)",
+        CMAKE_LUA_LIBRARIES = "$(LUA_LIBRARIES)",
         CMAKE_LUADIR = "$(LUADIR)",
         CMAKE_LIBDIR = "$(LIBDIR)",
         CMAKE_BUILD_TYPE = "RelWithDebInfo",