From 0eebe0c1a912273a324dc781f6b3b4a5616a8c8a Mon Sep 17 00:00:00 2001
From: Shengjing Zhu <zhsj@debian.org>
Date: Sun, 11 Aug 2019 18:06:47 +0800
Subject: [PATCH] Support override CLANG_RESOURCE_DIR

The result from clang commandline is something like
/usr/lib/llvm-7/lib/clang/7.0.1

Which means I need to recompile when the clang is upgraded to newer 7.x.x

However the system has a convenient symlink, which is
/usr/include/clang/7.
---
 CMakeLists.txt | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index baaa6a39..278e0735 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -120,22 +120,24 @@ endif()
 
 # Find Clang resource directory with Clang executable.
 
-find_program(CLANG_EXECUTABLE clang)
-if(NOT CLANG_EXECUTABLE)
-  message(FATAL_ERROR "clang executable not found.")
-endif()
+if(NOT CLANG_RESOURCE_DIR)
+  find_program(CLANG_EXECUTABLE clang)
+  if(NOT CLANG_EXECUTABLE)
+    message(FATAL_ERROR "clang executable not found.")
+  endif()
 
-execute_process(
-  COMMAND ${CLANG_EXECUTABLE} -print-resource-dir
-  RESULT_VARIABLE CLANG_FIND_RESOURCE_DIR_RESULT
-  OUTPUT_VARIABLE CLANG_RESOURCE_DIR
-  ERROR_VARIABLE CLANG_FIND_RESOURCE_DIR_ERROR
-  OUTPUT_STRIP_TRAILING_WHITESPACE
-)
+  execute_process(
+    COMMAND ${CLANG_EXECUTABLE} -print-resource-dir
+    RESULT_VARIABLE CLANG_FIND_RESOURCE_DIR_RESULT
+    OUTPUT_VARIABLE CLANG_RESOURCE_DIR
+    ERROR_VARIABLE CLANG_FIND_RESOURCE_DIR_ERROR
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+  )
 
-if(CLANG_FIND_RESOURCE_DIR_RESULT)
-  message(FATAL_ERROR "Error retrieving Clang resource directory with Clang \
-          executable. Output:\n ${CLANG_FIND_RESOURCE_DIR_ERROR}")
+  if(CLANG_FIND_RESOURCE_DIR_RESULT)
+    message(FATAL_ERROR "Error retrieving Clang resource directory with Clang \
+            executable. Output:\n ${CLANG_FIND_RESOURCE_DIR_ERROR}")
+  endif()
 endif()
 
 set_property(SOURCE src/utils.cc APPEND PROPERTY COMPILE_DEFINITIONS