(cmake) allow protobuf min version to be user-settable

Author: uatuko

cmake/dependencies.cmake

@@ -3,7 +3,7 @@ include(FetchContent)
 set(LIBUV_MINVERSION 1.46.0)
 set(BOOST_MINVERSION 1.81)
 set(NGHTTP2_MINVERSION 1.64.0)
-set(PROTOBUF_MINVERSION 3.15.0)
+set(PROTOBUF_MINVERSION 3.15.0 CACHE STRING "Protobuf version")
 set(FMT_MINVERSION 10.1.1)
 set(GTEST_MINVERSION 1.15.2)