Index: cmake/modules/AddSphinxTarget.cmake
===================================================================
--- cmake/modules/AddSphinxTarget.cmake
+++ cmake/modules/AddSphinxTarget.cmake
@@ -48,10 +48,15 @@
     # Handle installation
     if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
       if (builder STREQUAL man)
+        if (CMAKE_INSTALL_MANDIR)
+          set(INSTALL_MANDIR ${CMAKE_INSTALL_MANDIR}/)
+        else()
+          set(INSTALL_MANDIR share/man/)
+        endif()
         # FIXME: We might not ship all the tools that these man pages describe
         install(DIRECTORY "${SPHINX_BUILD_DIR}/" # Slash indicates contents of
                 COMPONENT "${project}-sphinx-man"
-                DESTINATION share/man/man1)
+                DESTINATION ${INSTALL_MANDIR}man1)
 
       elseif (builder STREQUAL html)
         string(TOUPPER "${project}" project_upper)