[cmake] Use new GetSVN.cmake SOURCE_DIRS parameter

[modocache]

Summary

Depends on LLVM https://reviews.llvm.org/D35132.

Instead of the old FIRST_SOURCE_DIR/FIRST_NAME,
SECOND_SOURCE_DIR/SECOND_NAME parameters, use the new
SOURCE_DIRS/NAMES list parameter. This allows the old parameters to
be deleted.

Test Plan:

1. Perform a clean build of Clang, verify that clang --version still prints the correct LLVM and Clang revision information.
2. Apply this patch to use the new arguments, then perform another clean build. clang --version should still print the correct revision information.

[beanz]

Since the dependent patch landed, this LGTM too.

lib/Basic/CMakeLists.txt

 
 set(get_svn_script "${LLVM_CMAKE_PATH}/GetSVN.cmake")
 
 if(DEFINED llvm_vc AND DEFINED clang_vc)
   # Create custom target to generate the VC revision include.
   add_custom_command(OUTPUT "${version_inc}"
     DEPENDS "${llvm_vc}" "${clang_vc}" "${get_svn_script}"
     COMMAND
-    ${CMAKE_COMMAND} "-DFIRST_SOURCE_DIR=${LLVM_MAIN_SRC_DIR}"
-                     "-DFIRST_NAME=LLVM"
-                     "-DSECOND_SOURCE_DIR=${CLANG_SOURCE_DIR}"
-                     "-DSECOND_NAME=SVN"
+    ${CMAKE_COMMAND} "-DSOURCE_DIRS=${LLVM_MAIN_SRC_DIR}\;${CLANG_SOURCE_DIR}"
+                     "-DNAMES=LLVM\;SVN"
                      "-DHEADER_FILE=${version_inc}"
                      -P "${get_svn_script}")
 
   # Mark the generated header as being generated.
   set_source_files_properties("${version_inc}"
     PROPERTIES GENERATED TRUE
                HEADER_FILE_ONLY TRUE)