Alter outdated(?) way of doing things.

If this ends up not working either, we should propbably rely on the (same) alteration in the generate step instead.

CURA-12675

Author: rburema

conanfile.py

@@ -137,7 +137,7 @@ def generate(self):
     def build(self):
         cmake = CMake(self)
 
-        cmake.definitions["_DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR"] = 1
+        cmake.compiler_definitions["_DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR"] = 1
 
         cmake.configure()
         cmake.build()