add --embed to $PYTHON_LD_FLAGS and strip a preceding whitespace to conform to CMP0004

--- a/test/pytest/src/CMakeLists.txt
+++ b/test/pytest/src/CMakeLists.txt
@@ -56,11 +56,12 @@ find_package(Python 3.11 REQUIRED
 if(UNIX)
     execute_process(
         COMMAND 
-            python3-config --ldflags 
+            python3-config --embed --ldflags
         OUTPUT_VARIABLE 
             PYTHON_LD_FLAGS 
         OUTPUT_STRIP_TRAILING_WHITESPACE
     )
+    string(STRIP ${PYTHON_LD_FLAGS} PYTHON_LD_FLAGS)
 endif()
 
 target_link_libraries(${TARGET_NAME} PRIVATE