confgen.py: Escape special characters for cmake

Closes https://github.com/espressif/esp-idf/issues/4751

tools/kconfig_new/confgen.py

@@ -408,6 +408,8 @@ def write_cmake(deprecated_options, config, filename):
                 val = sym.str_value
                 if sym.orig_type in (kconfiglib.BOOL, kconfiglib.TRISTATE) and val == "n":
                     val = ""  # write unset values as empty variables
+                elif sym.orig_type == kconfiglib.STRING:
+                    val = kconfiglib.escape(val)
                 write("set({}{} \"{}\")\n".format(
                     prefix, sym.name, val))