[cmake] fix worktrees GenerateSCMRev.cmake

Signed-off-by: lizzie <lizzie@eden-emu.dev>

CMakeModules/GenerateSCMRev.cmake

@@ -18,10 +18,16 @@ if (DEFINED GIT_RELEASE)
   set(BUILD_VERSION "${GIT_TAG}")
   set(GIT_REFSPEC "${GIT_RELEASE}")
   set(IS_DEV_BUILD false)
-else()
+elseif(DEFINED GIT_COMMIT)
   string(SUBSTRING ${GIT_COMMIT} 0 10 BUILD_VERSION)
   set(BUILD_VERSION "${BUILD_VERSION}-${GIT_REFSPEC}")
   set(IS_DEV_BUILD true)
+elseif(DEFINED GIT_REFSPEC)
+  set(BUILD_VERSION "${GIT_REFSPEC}")
+  set(IS_DEV_BUILD true)
+else()
+  set(BUILD_VERSION "scm-none")
+  set(IS_DEV_BUILD true)
 endif()
 
 set(GIT_DESC ${BUILD_VERSION})