Bug#979577: qtcreator: Clang Code Model no longer finds 'stddef.h' since version 4.14.0-2

[domin144@o2.pl <domin144@o2.pl>]

This patch works for me.

--- a/src/libs/clangsupport/CMakeLists.txt
+++ b/src/libs/clangsupport/CMakeLists.txt
@@ -5,8 +5,8 @@
   PUBLIC_DEPENDS Utils Sqlite Qt5::Core Qt5::Network
   PUBLIC_DEFINES
     CLANG_VERSION="${CLANG_VERSION}"
-    CLANG_INCLUDE_DIR="${IDE_LIBEXEC_PATH}/clang/lib/clang/${CLANG_VERSION}/include"
-    CLANG_BINDIR="${IDE_LIBEXEC_PATH}/clang/bin"
+    CLANG_INCLUDE_DIR="${LLVM_LIBRARY_DIR}/clang/${CLANG_VERSION}/include"
+    CLANG_BINDIR="${LLVM_TOOLS_BINARY_DIR}"
   DEFINES CLANGSUPPORT_BUILD_LIB
   PUBLIC_INCLUDES
     "${CMAKE_CURRENT_LIST_DIR}"