cmake/gcc: Don't use -nostdinc with toolchain picolibc

When using picolibc from the toolchain, we need to use the standard include
paths to make sure the library headers are found, especially for libstdc++.

Add toolchain picolibc to the list of cases for which this is the case.

Signed-off-by: Keith Packard <keithp@keithp.com>

cmake/compiler/gcc/compiler_flags.cmake

@@ -104,6 +104,7 @@ set_compiler_property(PROPERTY warning_error_coding_guideline
 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 CONFIG_HAS_ESPRESSIF_HAL AND
     NOT CONFIG_NATIVE_APPLICATION)