fix invalid platform type on linux build

Author: leafo

.github/workflows/binaries.yml

@@ -16,7 +16,7 @@ jobs:
       run: |
         curl -O https://www.lua.org/ftp/lua-5.1.5.tar.gz
         tar -xZf lua-5.1.5.tar.gz
-        cd lua-5.1.5; make PLAT=mingw
+        cd lua-5.1.5; make
 
     - name: Get LPeg
       run: |