[cmake] Exposes LLVM version number in the runtimes. (#84641)

This allows sharing the LLVM version number in libc++.

Author: mordante

cmake/Modules/LLVMVersion.cmake

@@ -0,0 +1,15 @@
+# The LLVM Version number information
+
+if(NOT DEFINED LLVM_VERSION_MAJOR)
+  set(LLVM_VERSION_MAJOR 19)
+endif()
+if(NOT DEFINED LLVM_VERSION_MINOR)
+  set(LLVM_VERSION_MINOR 0)
+endif()
+if(NOT DEFINED LLVM_VERSION_PATCH)
+  set(LLVM_VERSION_PATCH 0)
+endif()
+if(NOT DEFINED LLVM_VERSION_SUFFIX)
+  set(LLVM_VERSION_SUFFIX git)
+endif()
+

llvm/CMakeLists.txt

@@ -15,18 +15,7 @@ if(NOT LLVM_NO_INSTALL_NAME_DIR_FOR_BUILD_TREE)
   set(CMAKE_BUILD_WITH_INSTALL_NAME_DIR ON)
 endif()
 
-if(NOT DEFINED LLVM_VERSION_MAJOR)
-  set(LLVM_VERSION_MAJOR 19)
-endif()
-if(NOT DEFINED LLVM_VERSION_MINOR)
-  set(LLVM_VERSION_MINOR 0)
-endif()
-if(NOT DEFINED LLVM_VERSION_PATCH)
-  set(LLVM_VERSION_PATCH 0)
-endif()
-if(NOT DEFINED LLVM_VERSION_SUFFIX)
-  set(LLVM_VERSION_SUFFIX git)
-endif()
+include(${LLVM_COMMON_CMAKE_UTILS}/Modules/LLVMVersion.cmake)
 
 set_directory_properties(PROPERTIES LLVM_VERSION_MAJOR "${LLVM_VERSION_MAJOR}")
 

runtimes/CMakeLists.txt

@@ -6,6 +6,8 @@ set(LLVM_COMMON_CMAKE_UTILS "${CMAKE_CURRENT_SOURCE_DIR}/../cmake")
 include(${LLVM_COMMON_CMAKE_UTILS}/Modules/CMakePolicy.cmake
   NO_POLICY_SCOPE)
 
+include(${LLVM_COMMON_CMAKE_UTILS}/Modules/LLVMVersion.cmake)
+
 project(Runtimes C CXX ASM)
 
 list(INSERT CMAKE_MODULE_PATH 0