Add ENABLE_LEPTWIN option and default off

leftwin.c does not build on Windows Server 2019 targets but seems
that tesseract does not actually use it, so disable builds

CMakeLists.txt

@@ -71,7 +71,9 @@ option(ENABLE_JPEG "Enable JPEG support" ON)
 option(ENABLE_TIFF "Enable TIFF support" ON)
 option(ENABLE_WEBP "Enable WebP support" OFF)
 option(ENABLE_OPENJPEG "Enable OpenJPEG support" OFF)
-
+if(WIN32)
+  option(ENABLE_LEPTWIN "Build leptwin.c on Windows" OFF)
+endif()
 set(leptonica_INSTALL_CMAKE_DIR
     "lib/cmake/leptonica"
     CACHE STRING "Install destination for CMake package files")

src/CMakeLists.txt

@@ -11,6 +11,13 @@
 file(GLOB hdr "*.h")
 file(GLOB src "*.c")
 
+if (NOT WIN32 OR NOT ENABLE_LEPTWIN)
+   # leptwin.c can be a problem to compile on some environments
+   # the main use of this module (tesseract) no longer seems to need it
+   list(FILTER src EXCLUDE REGEX .*leptwin.c)
+   list(FILTER hdr EXCLUDE REGEX .*leptwin.h)
+endif()
+
 string(REPLACE "-O3" "-O2" CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}")
 
 add_library                     (leptonica ${src} ${hdr})