CMake ExternalProject_Add rebuilds every time

Question

I have OpenSSL as a part of my CMake project. Since it does not have its own CMake file I build it as an ExternalProject. Unfortunately every time I rebuild my project the ExternalProject is also rebuilt and it is the biggest and slowest part by far.

How can I avoid that ExternalProject is being rebuilt every time?

I tried BUILD_ALWAYS = false but it did not help. OpenSSL has to be built from sources as a static library.

Answer 1

Add empty UPDATE_COMMAND:

ExternalProject_Add(
  ...
  UPDATE_COMMAND ""
  ...
)