[cmake] Respect LLVM_CMAKE_PATH in stand-alone builds for GetSVN.cmake

[mgorny]

Summary

Use LLVM_CMAKE_PATH to spawn GetSVN.cmake rather than the source path
when stand-alone build is performed, to remove the unnecessary
dependency on LLVM sources and use the installed version instead.
Non-standalone builds retain the old behavior.

[beanz]

Maybe we should define LLVM_CMAKE_PATH in llvm's CMakeLists.txt so that we don't need a condition here or in clang where we do the same thing?

[krytarowski]

This change makes sense for stand-alone builds, but if it's possible to remove branching in this CMake file - please go for it.

[mgorny]

LLVM_CMAKE_PATH posted as D25724.

[mgorny]

Now handled as a followup of D25724.

source/CMakeLists.txt

foreach(file
   if(EXISTS "${file}")
     set(lldb_vc "${file}")
     break()
   endif()
 endforeach()
 
 if(DEFINED lldb_vc)
   set(version_inc "${CMAKE_CURRENT_BINARY_DIR}/SVNVersion.inc")
+  if(LLDB_BUILT_STANDALONE)
+    set(get_svn_script "${LLVM_CMAKE_PATH}/GetSVN.cmake")
+  else()
     set(get_svn_script "${LLVM_MAIN_SRC_DIR}/cmake/modules/GetSVN.cmake")
+  endif()
 
   # Create custom target to generate the VC revision include.
   add_custom_command(OUTPUT "${version_inc}"
     DEPENDS "${lldb_vc}" "${get_svn_script}"
     COMMAND
     ${CMAKE_COMMAND} "-DFIRST_SOURCE_DIR=${LLDB_SOURCE_DIR}"
                      "-DFIRST_NAME=LLDB"
                      "-DHEADER_FILE=${version_inc}"