Windows: do not skip building `yangre`

It looks like I excluded this by mistake; the `getopt` library is
already used by `yanglint` anyway.

Fixes: 2e3f935e MSVC: tools: disable interactive tools
diff --git a/tools/CMakeLists.txt b/tools/CMakeLists.txt
index 94b4eed..b92f80c 100644
--- a/tools/CMakeLists.txt
+++ b/tools/CMakeLists.txt
@@ -1,11 +1,15 @@
 # config file for tools
 configure_file(${PROJECT_SOURCE_DIR}/tools/config.h.in ${PROJECT_BINARY_DIR}/tools/config.h @ONLY)
 
-add_subdirectory(lint)
-if(NOT WIN32)
-    add_subdirectory(re)
+if(WIN32)
+    find_library(GETOPT_LIBRARY NAMES getopt REQUIRED)
+    find_path(GETOPT_INCLUDE_DIR NAMES getopt.h REQUIRED)
+    message(STATUS "Found <getopt.h> at ${GETOPT_INCLUDE_DIR}, library at ${GETOPT_LIBRARY}")
 endif()
 
+add_subdirectory(lint)
+add_subdirectory(re)
+
 set(format_sources
     ${format_sources}
     PARENT_SCOPE)