From 1310d43380c7e214d3e3f5c87c402983cb543521 Mon Sep 17 00:00:00 2001
From: Peter Kokot <peterkokot@gmail.com>
Date: Sun, 22 Dec 2024 00:11:28 +0100
Subject: [PATCH] FindFlex: Add COMMAND_EXPAND_LISTS to remove empty arguments

This is a follow-up of 3ffc8a6b613e5b31ed75d25b28b86a5ebabdf9ce

When using generator expressions in the COMPILE_FLAGS argument, and the
generator expression expands to an empty string, command gets an empty
argument with double quotes where flex command-line tool errors out
with `/usr/bin/flex: can't open` error. This removes empty arguments
from the created flex command.
---
 Modules/FindFLEX.cmake | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Modules/FindFLEX.cmake b/Modules/FindFLEX.cmake
index e67e931125..e32886d8af 100644
--- a/Modules/FindFLEX.cmake
+++ b/Modules/FindFLEX.cmake
@@ -217,7 +217,8 @@ if(FLEX_EXECUTABLE)
         VERBATIM
         DEPENDS ${_flex_INPUT}
         COMMENT "[FLEX][${Name}] Building scanner with ${_flex_EXE_NAME_WE} ${FLEX_VERSION}"
-        WORKING_DIRECTORY ${_flex_WORKING_DIR})
+        WORKING_DIRECTORY ${_flex_WORKING_DIR}
+        COMMAND_EXPAND_LISTS)
 
       set(FLEX_${Name}_DEFINED TRUE)
       set(FLEX_${Name}_OUTPUTS ${_flex_TARGET_OUTPUTS})