build protobuf without zlib

CMakeLists.txt

@@ -162,6 +162,11 @@ if("${gRPC_PROTOBUF_PROVIDER}" STREQUAL "module")
   if(NOT protobuf_BUILD_TESTS)
     set(protobuf_BUILD_TESTS OFF CACHE BOOL "Build protobuf tests")
   endif()
+  # Disable building protobuf with zlib. Building protobuf with zlib breaks
+  # the build if zlib is not installed on the system.
+  if(NOT protobuf_WITH_ZLIB)
+    set(protobuf_WITH_ZLIB OFF CACHE BOOL "Build protobuf with zlib.")
+  endif()
   if(NOT PROTOBUF_ROOT_DIR)
     set(PROTOBUF_ROOT_DIR ${CMAKE_CURRENT_SOURCE_DIR}/third_party/protobuf)
   endif()

templates/CMakeLists.txt.template

@@ -207,6 +207,11 @@
     if(NOT protobuf_BUILD_TESTS)
       set(protobuf_BUILD_TESTS OFF CACHE BOOL "Build protobuf tests")
     endif()
+    # Disable building protobuf with zlib. Building protobuf with zlib breaks
+    # the build if zlib is not installed on the system.
+    if(NOT protobuf_WITH_ZLIB)
+      set(protobuf_WITH_ZLIB OFF CACHE BOOL "Build protobuf with zlib.")
+    endif()
     if(NOT PROTOBUF_ROOT_DIR)
       set(PROTOBUF_ROOT_DIR <%text>${CMAKE_CURRENT_SOURCE_DIR}</%text>/third_party/protobuf)
     endif()