Fix handling of tools.build:defines for multiconfig CMake (#15921)

conan/tools/cmake/toolchain/blocks.py

@@ -154,7 +154,7 @@ def context(self):
 
         if not config_dict:
             return None
-        
+
         vs_debugger_path = ""
         for config, value in config_dict.items():
             vs_debugger_path += f"$<$<CONFIG:{config}>:{value}>"
@@ -613,7 +613,10 @@ class ExtraFlagsBlock(Block):
         {% endif %}
         {% if defines %}
         {% if config %}
-        add_compile_definitions($<$<CONFIG:{{config}}>:{% for define in defines %}" {{ define }}"{% endfor %}>)
+        add_compile_definitions(
+        {%- for define in defines %}
+        "$<$<CONFIG:{{config}}>:{{define}}>"
+        {%- endfor -%})
         {% else %}
         add_compile_definitions({% for define in defines %} "{{ define }}"{% endfor %})
         {% endif %}