twister: remove spurious quoting of EXTRA_xFLAGS=-Werror

Testing shows cmake is invoked directly, not through a shell.

Fixes commit 5092541e2b ("sanitycheck: disable erroring on warnings").
Note EXTRA_AFLAGS was quoted only on the left side!

Signed-off-by: Marc Herbert <marc.herbert@intel.com>

scripts/pylib/twister/twisterlib.py

@@ -2149,9 +2149,9 @@ class CMake():
         cmake_args = [
             f'-B{self.build_dir}',
             f'-S{self.source_dir}',
-            f'-DEXTRA_CFLAGS="{cflags}"',
-            f'-DEXTRA_AFLAGS="{aflags}',
-            f'-DEXTRA_LDFLAGS="{ldflags}"',
+            f'-DEXTRA_CFLAGS={cflags}',
+            f'-DEXTRA_AFLAGS={aflags}',
+            f'-DEXTRA_LDFLAGS={ldflags}',
             f'-DEXTRA_GEN_DEFINES_ARGS={gen_defines_args}',
             f'-G{self.generator}'
         ]