Proposed workaround for [b5ced5865b]: newer MinGW compilers can link directory to the zlib dll, hopefully older MinGW's which cannot do that are obsolete now. For now, leave 64-bit as-is.

win/Makefile.in

@@ -459,10 +459,11 @@ ${TEST_DLL_FILE}: ${TCL_STUB_LIB_FILE} ${TCLTEST_OBJS}
 
 # use pre-built zlib1.dll
 ${ZLIB_DLL_FILE}: ${TCL_STUB_LIB_FILE}
-	@if test "@ZLIB_LIBS@set" != "${ZLIB_DIR}/win32/zdll.libset" ; then \
+	@if test "@ZLIB_LIBS@set" != "-L. -lzset" -a "@ZLIB_LIBS@set" != "${ZLIB_DIR}/win32/zdll.libset"; then \
 		$(COPY) $(ZLIB_DIR)/win64/${ZLIB_DLL_FILE} ${ZLIB_DLL_FILE}; \
 	else \
 		$(COPY) $(ZLIB_DIR)/win32/${ZLIB_DLL_FILE} ${ZLIB_DLL_FILE}; \
+		$(COPY) $(ZLIB_DIR)/win32/${ZLIB_DLL_FILE} libz.dll.a; \
 	fi;
 
 # Add the object extension to the implicit rules. By default .obj is not

win/configure

@@ -4377,7 +4377,17 @@ fi
 
 else
 
-    ZLIB_LIBS=\${ZLIB_DIR}/win32/zdll.lib
+    if test "$GCC" == "yes"; then
+
+      ZLIB_LIBS="-L. -lz"
+
+
+else
+
+      ZLIB_LIBS=\${ZLIB_DIR}/win32/zdll.lib
+
+
+fi
 
 
 fi

win/configure.in

@@ -135,7 +135,11 @@ AS_IF([test "$tcl_ok" = "yes"], [
       AC_SUBST(ZLIB_LIBS,[\${ZLIB_DIR}/win64/zdll.lib])
     ])
   ], [
-    AC_SUBST(ZLIB_LIBS,[\${ZLIB_DIR}/win32/zdll.lib])
+    AS_IF([test "$GCC" == "yes"],[
+      AC_SUBST(ZLIB_LIBS,["-L. -lz"])
+    ], [
+      AC_SUBST(ZLIB_LIBS,[\${ZLIB_DIR}/win32/zdll.lib])
+    ])
   ])
 ], [
   AC_SUBST(ZLIB_OBJS,[\${ZLIB_OBJS}])