Fix build on case-sensitive filesystems
https://github.com/Gnucash/gnucash/pull/356
https://github.com/Gnucash/gnucash/commit/075021a88d2001546754097de8880251a7e085a0
--- CMakeLists.txt.orig	2018-04-30 13:58:18.000000000 -0500
+++ CMakeLists.txt	2018-05-26 14:10:34.000000000 -0500
@@ -526,7 +526,7 @@
 
 if (APPLE)
   include (CheckCCompilerFlag)
-  include (CheckCxxCompilerFlag)
+  include (CheckCXXCompilerFlag)
   Check_CXX_Compiler_Flag(-Wno-unused-local-typedef, have_wno_ult)
   if (have_wno_ult)
     SET( CMAKE_CXX_FLAGS "-Wno-unused-local-typedef -Wmissing-prototypes ${CMAKE_CXX_FLAGS}")