Build MinGW import library, too.

Thanks to Tarnyko.

src/Makefile

@@ -219,6 +219,7 @@ TARGET_SONAME= libluajit-$(ABIVER).so.$(MAJVER)
 TARGET_DYLIBNAME= libluajit-$(ABIVER).$(MAJVER).dylib
 TARGET_DYLIBPATH= $(TARGET_LIBPATH)/$(TARGET_DYLIBNAME)
 TARGET_DLLNAME= lua$(NODOTABIVER).dll
+TARGET_DLLDOTANAME= libluajit-$(ABIVER).dll.a
 TARGET_XSHLDFLAGS= -shared -fPIC -Wl,-soname,$(TARGET_SONAME)
 TARGET_DYNXLDOPTS=
 
@@ -293,7 +294,7 @@ endif
 TARGET_SYS?= $(HOST_SYS)
 ifeq (Windows,$(TARGET_SYS))
   TARGET_STRIP+= --strip-unneeded
-  TARGET_XSHLDFLAGS= -shared
+  TARGET_XSHLDFLAGS= -shared -Wl,--out-implib,$(TARGET_DLLDOTANAME)
   TARGET_DYNXLDOPTS=
   HOST_RM= del
 else