Add CMake build support for version suffixes

Summary:
CMake project versions can only be dot-separated integers. This diff allows us
to additionally specify a suffix, e.g. `-rc3`.

Reviewed By: dulinriley

Differential Revision: D20776302

fbshipit-source-id: ae9b7a4cdd00d955084a6f9c117e4aff32baf60f

CMakeLists.txt

@@ -57,6 +57,8 @@ endif()
 project(Hermes
         VERSION 0.4.0
         LANGUAGES C CXX)
+# Optional suffix like "-rc3"
+set(VERSION_SUFFIX "")
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules/")
 
@@ -65,7 +67,7 @@ set(LLVH_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/external/llvh)
 include(Hermes)
 include(Lit)
 
-set(HERMES_RELEASE_VERSION ${PROJECT_VERSION})
+set(HERMES_RELEASE_VERSION ${PROJECT_VERSION}${VERSION_SUFFIX})
 
 # Project options.
 set(HERMESVM_GCKIND NONCONTIG_GENERATIONAL