[LyX/master] Cmake build: Use correct include if using internal hunspell

[Kornel Benko]

commit b399cfc7a27a484c519cf76fe9fac8cc4435a66a
Author: Kornel Benko <kornel at lyx.org>
Date:   Fri Feb 28 21:48:54 2020 +0100

    Cmake build: Use correct include if using internal hunspell
    
    This way also "HAVE_HUNSPELL_CXXABI" is correctly set to 1
---
 3rdparty/hunspell/CMakeLists.txt |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/3rdparty/hunspell/CMakeLists.txt b/3rdparty/hunspell/CMakeLists.txt
index 90dae46..c690938 100644
--- a/3rdparty/hunspell/CMakeLists.txt
+++ b/3rdparty/hunspell/CMakeLists.txt
@@ -58,7 +58,7 @@ add_definitions(-DHUNSPELL_STATIC)
 add_library(hunspell STATIC ${HEADERS} ${SRCS} ${HUNCONFIG})
 
 set(HUNSPELL_LIBRARY hunspell CACHE STRING "Hunspell library" FORCE)
-set(HUNSPELL_INCLUDE_DIR ${SRCDIR} CACHE STRING "Hunspell include dir" FORCE)
+set(HUNSPELL_INCLUDE_DIR "${SRCDIR}/hunspell" CACHE STRING "Hunspell include dir" FORCE)
 set(HUNSPELL_FOUND CACHE STRING "Hunspell found" FORCE)
 
 set_target_properties(hunspell PROPERTIES