(build) switch static-in source luaJIT to 2.1-rc3

Pending a transition of the packaging in voidlinux etc. to use the more
recent luaJIT, this change helps to test that out in beforehand. Resynch
the external/git repository if this causes any issues.

Author: letoram

src/CMakeLists.txt

@@ -366,6 +366,7 @@ if (NOT DISABLE_JIT)
 			SOURCE_DIR ${CMAKE_CURRENT_BINARY_DIR}/luajit
 			GIT_REPOSITORY "${EXTERNAL_SRC_DIR}/git/luajit"
 			CONFIGURE_COMMAND ""
+			GIT_TAG "v2.1.0-beta3"
 			UPDATE_COMMAND ""
 			INSTALL_COMMAND ""
 			BUILD_IN_SOURCE 1