cmake: compiler/gcc: skip nostdinc property for xt-clang

Xtensa toolchain xt-clang needs similar treatment to xcc in
terms of nostdinc and nostdinc_include, so add it to the if
block to exclude these by default.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

Author: dcpleung

cmake/compiler/gcc/compiler_flags.cmake

@@ -116,6 +116,7 @@ set_compiler_property(PROPERTY cstd -std=)
 if (NOT CONFIG_NEWLIB_LIBC AND
     NOT (CONFIG_PICOLIBC AND NOT CONFIG_PICOLIBC_USE_MODULE) AND
     NOT COMPILER STREQUAL "xcc" AND
+    NOT COMPILER STREQUAL "xt-clang" AND
     NOT CONFIG_HAS_ESPRESSIF_HAL AND
     NOT CONFIG_NATIVE_BUILD)
   set_compiler_property(PROPERTY nostdinc -nostdinc)