cmake, refactor: Introduce SetLibtoolAbiVersion module

cmake/SetLibtoolAbiVersion.cmake

@@ -0,0 +1,28 @@
+# This emulates Libtool to make sure Libtool and CMake agree on the ABI version,
+# see below "Calculate the version variables" in autotools-aux/ltmain.sh.
+function(set_libtool_abi_version target current revision age)
+  math(EXPR _soversion "${current} - ${age}")
+  set_target_properties(${target} PROPERTIES
+    SOVERSION ${_soversion}
+  )
+  if(CMAKE_SYSTEM_NAME MATCHES "^(Linux|FreeBSD)$")
+    set_target_properties(${target} PROPERTIES
+      VERSION ${_soversion}.${age}.${revision}
+    )
+  elseif(APPLE)
+    math(EXPR _compatibility "${current} + 1")
+    set_target_properties(${target} PROPERTIES
+      MACHO_COMPATIBILITY_VERSION ${_compatibility}
+      MACHO_CURRENT_VERSION ${_compatibility}.${revision}
+    )
+  elseif(CMAKE_SYSTEM_NAME STREQUAL "Windows")
+    set(_windows_name "secp256k1")
+    if(MSVC)
+      set(_windows_name "${PROJECT_NAME}")
+    endif()
+    set_target_properties(${target} PROPERTIES
+      ARCHIVE_OUTPUT_NAME "${_windows_name}"
+      RUNTIME_OUTPUT_NAME "${_windows_name}-${_soversion}"
+    )
+  endif()
+endfunction()